When trying to build the 10.6.0-rc1 release on FreeBSD it spits out the error below.

  CXX      api/libclover_la-interop.lo
In file included from api/interop.cpp:24:
In file included from ./core/event.hpp:29:
In file included from ./core/object.hpp:32:
./core/error.hpp:55:38: error: implicit instantiation of undefined template
      'std::__1::basic_string<char, std::__1::char_traits<char>,
      std::__1::allocator<char> >'
      error(cl_int code, std::string what = "") :
                                     ^
/usr/include/c++/v1/iosfwd:188:33: note: template is declared here
    class _LIBCPP_TYPE_VIS_ONLY basic_string;
                                ^
In file included from api/interop.cpp:24:
In file included from ./core/event.hpp:29:
In file included from ./core/object.hpp:32:
./core/error.hpp:69:38: error: reference to type 'const std::string' (aka 'const
      basic_string<char, char_traits<char>, allocator<char> >') could not bind
      to an lvalue of type 'const char [1]'
      build_error(const std::string &what = "") :
                                     ^      ~~
./core/error.hpp:69:38: note: passing argument to parameter 'what' here
./core/error.hpp:70:44: error: implicit instantiation of undefined template
      'std::__1::basic_string<char, std::__1::char_traits<char>,
      std::__1::allocator<char> >'
         error(CL_COMPILE_PROGRAM_FAILURE, what) {
                                           ^
/usr/include/c++/v1/iosfwd:188:33: note: template is declared here
    class _LIBCPP_TYPE_VIS_ONLY basic_string;
                                ^
In file included from api/interop.cpp:24:
In file included from ./core/event.hpp:29:
In file included from ./core/object.hpp:32:
./core/error.hpp:80:40: error: implicit instantiation of undefined template
      'std::__1::basic_string<char, std::__1::char_traits<char>,
      std::__1::allocator<char> >'
      invalid_object_error(std::string what = "") :
                                       ^
/usr/include/c++/v1/iosfwd:188:33: note: template is declared here
    class _LIBCPP_TYPE_VIS_ONLY basic_string;
                                ^
In file included from api/interop.cpp:24:
In file included from ./core/event.hpp:29:
In file included from ./core/object.hpp:32:
./core/error.hpp:87:40: error: implicit instantiation of undefined template
      'std::__1::basic_string<char, std::__1::char_traits<char>,
      std::__1::allocator<char> >'
      invalid_object_error(std::string what = "") :
                                       ^
/usr/include/c++/v1/iosfwd:188:33: note: template is declared here
    class _LIBCPP_TYPE_VIS_ONLY basic_string;
                                ^
In file included from api/interop.cpp:24:
In file included from ./core/event.hpp:29:
In file included from ./core/object.hpp:32:
./core/error.hpp:94:40: error: implicit instantiation of undefined template
      'std::__1::basic_string<char, std::__1::char_traits<char>,
      std::__1::allocator<char> >'
      invalid_object_error(std::string what = "") :
                                       ^
/usr/include/c++/v1/iosfwd:188:33: note: template is declared here
    class _LIBCPP_TYPE_VIS_ONLY basic_string;
                                ^
In file included from api/interop.cpp:24:
In file included from ./core/event.hpp:29:
In file included from ./core/object.hpp:32:
./core/error.hpp:101:40: error: implicit instantiation of undefined template
      'std::__1::basic_string<char, std::__1::char_traits<char>,
      std::__1::allocator<char> >'
      invalid_object_error(std::string what = "") :
                                       ^
/usr/include/c++/v1/iosfwd:188:33: note: template is declared here
    class _LIBCPP_TYPE_VIS_ONLY basic_string;
                                ^
In file included from api/interop.cpp:24:
In file included from ./core/event.hpp:29:
In file included from ./core/object.hpp:32:
./core/error.hpp:108:40: error: implicit instantiation of undefined template
      'std::__1::basic_string<char, std::__1::char_traits<char>,
      std::__1::allocator<char> >'
      invalid_object_error(std::string what = "") :
                                       ^
/usr/include/c++/v1/iosfwd:188:33: note: template is declared here
    class _LIBCPP_TYPE_VIS_ONLY basic_string;
                                ^
In file included from api/interop.cpp:24:
In file included from ./core/event.hpp:29:
In file included from ./core/object.hpp:32:
./core/error.hpp:115:40: error: implicit instantiation of undefined template
      'std::__1::basic_string<char, std::__1::char_traits<char>,
      std::__1::allocator<char> >'
      invalid_object_error(std::string what = "") :
                                       ^
/usr/include/c++/v1/iosfwd:188:33: note: template is declared here
    class _LIBCPP_TYPE_VIS_ONLY basic_string;
                                ^
In file included from api/interop.cpp:24:
In file included from ./core/event.hpp:29:
In file included from ./core/object.hpp:32:
./core/error.hpp:122:40: error: implicit instantiation of undefined template
      'std::__1::basic_string<char, std::__1::char_traits<char>,
      std::__1::allocator<char> >'
      invalid_object_error(std::string what = "") :
                                       ^
/usr/include/c++/v1/iosfwd:188:33: note: template is declared here
    class _LIBCPP_TYPE_VIS_ONLY basic_string;
                                ^
In file included from api/interop.cpp:24:
In file included from ./core/event.hpp:29:
In file included from ./core/object.hpp:32:
./core/error.hpp:129:40: error: implicit instantiation of undefined template
      'std::__1::basic_string<char, std::__1::char_traits<char>,
      std::__1::allocator<char> >'
      invalid_object_error(std::string what = "") :
                                       ^
/usr/include/c++/v1/iosfwd:188:33: note: template is declared here
    class _LIBCPP_TYPE_VIS_ONLY basic_string;
                                ^
In file included from api/interop.cpp:24:
In file included from ./core/event.hpp:29:
In file included from ./core/object.hpp:32:
./core/error.hpp:136:40: error: implicit instantiation of undefined template
      'std::__1::basic_string<char, std::__1::char_traits<char>,
      std::__1::allocator<char> >'
      invalid_object_error(std::string what = "") :
                                       ^
/usr/include/c++/v1/iosfwd:188:33: note: template is declared here
    class _LIBCPP_TYPE_VIS_ONLY basic_string;
                                ^
In file included from api/interop.cpp:24:
In file included from ./core/event.hpp:29:
In file included from ./core/object.hpp:32:
./core/error.hpp:143:40: error: implicit instantiation of undefined template
      'std::__1::basic_string<char, std::__1::char_traits<char>,
      std::__1::allocator<char> >'
      invalid_object_error(std::string what = "") :
                                       ^
/usr/include/c++/v1/iosfwd:188:33: note: template is declared here
    class _LIBCPP_TYPE_VIS_ONLY basic_string;
                                ^
In file included from api/interop.cpp:24:
In file included from ./core/event.hpp:29:
In file included from ./core/object.hpp:32:
./core/error.hpp:150:40: error: implicit instantiation of undefined template
      'std::__1::basic_string<char, std::__1::char_traits<char>,
      std::__1::allocator<char> >'
      invalid_object_error(std::string what = "") :
                                       ^
/usr/include/c++/v1/iosfwd:188:33: note: template is declared here
    class _LIBCPP_TYPE_VIS_ONLY basic_string;
                                ^
In file included from api/interop.cpp:24:
In file included from ./core/event.hpp:29:
In file included from ./core/object.hpp:32:
./core/error.hpp:157:40: error: implicit instantiation of undefined template
      'std::__1::basic_string<char, std::__1::char_traits<char>,
      std::__1::allocator<char> >'
      invalid_object_error(std::string what = "") :
                                       ^
/usr/include/c++/v1/iosfwd:188:33: note: template is declared here
    class _LIBCPP_TYPE_VIS_ONLY basic_string;
                                ^
In file included from api/interop.cpp:24:
In file included from ./core/event.hpp:29:
In file included from ./core/object.hpp:32:
./core/error.hpp:164:40: error: implicit instantiation of undefined template
      'std::__1::basic_string<char, std::__1::char_traits<char>,
      std::__1::allocator<char> >'
      invalid_object_error(std::string what = "") :
                                       ^
/usr/include/c++/v1/iosfwd:188:33: note: template is declared here
    class _LIBCPP_TYPE_VIS_ONLY basic_string;
                                ^
In file included from api/interop.cpp:24:
In file included from ./core/event.hpp:29:
In file included from ./core/object.hpp:32:
./core/error.hpp:171:40: error: implicit instantiation of undefined template
      'std::__1::basic_string<char, std::__1::char_traits<char>,
      std::__1::allocator<char> >'
      invalid_object_error(std::string what = "") :
                                       ^
/usr/include/c++/v1/iosfwd:188:33: note: template is declared here
    class _LIBCPP_TYPE_VIS_ONLY basic_string;
                                ^
In file included from api/interop.cpp:24:
In file included from ./core/event.hpp:29:
In file included from ./core/object.hpp:32:
./core/error.hpp:178:40: error: implicit instantiation of undefined template
      'std::__1::basic_string<char, std::__1::char_traits<char>,
      std::__1::allocator<char> >'
      invalid_object_error(std::string what = "") :
                                       ^
/usr/include/c++/v1/iosfwd:188:33: note: template is declared here
    class _LIBCPP_TYPE_VIS_ONLY basic_string;
                                ^
In file included from api/interop.cpp:24:
In file included from ./core/event.hpp:29:
In file included from ./core/object.hpp:32:
./core/error.hpp:185:40: error: implicit instantiation of undefined template
      'std::__1::basic_string<char, std::__1::char_traits<char>,
      std::__1::allocator<char> >'
      invalid_object_error(std::string what = "") :
                                       ^
/usr/include/c++/v1/iosfwd:188:33: note: template is declared here
    class _LIBCPP_TYPE_VIS_ONLY basic_string;
                                ^
fatal error: too many errors emitted, stopping now [-ferror-limit=]
20 errors generated.