I am getting the following error on Ubuntu (every supported release) since recent commits.

Full build log, including configure options here: https://launchpadlibrarian.net/361314745/buildlog_ubuntu-xenial-amd64.mesa_18.1~git1803200730.9a243e~oibaf~x_BUILDING.txt.gz

libtool: compile:  gcc -DPACKAGE_NAME=\"Mesa\" -DPACKAGE_TARNAME=\"mesa\" -DPACKAGE_VERSION=\"18.1.0-devel\" "-DPACKAGE_STRING=\"Mesa 18.1.0-devel\"" "-DPACKAGE_BUGREPORT=\"https://bugs.freedesktop.org/enter_bug.cgi?product=Mesa\"" -DPACKAGE_URL=\"\" -DPACKAGE=\"mesa\" -DVERSION=\"18.1.0-devel\" -DSTDC_HEADERS=1 -DHAVE_SYS_TYPES_H=1 -DHAVE_SYS_STAT_H=1 -DHAVE_STDLIB_H=1 -DHAVE_STRING_H=1 -DHAVE_MEMORY_H=1 -DHAVE_STRINGS_H=1 -DHAVE_INTTYPES_H=1 -DHAVE_STDINT_H=1 -DHAVE_UNISTD_H=1 -DHAVE_DLFCN_H=1 -DLT_OBJDIR=\".libs/\" -DYYTEXT_POINTER=1 -DHAVE___BUILTIN_BSWAP32=1 -DHAVE___BUILTIN_BSWAP64=1 -DHAVE___BUILTIN_CLZ=1 -DHAVE___BUILTIN_CLZLL=1 -DHAVE___BUILTIN_CTZ=1 -DHAVE___BUILTIN_EXPECT=1 -DHAVE___BUILTIN_FFS=1 -DHAVE___BUILTIN_FFSLL=1 -DHAVE___BUILTIN_POPCOUNT=1 -DHAVE___BUILTIN_POPCOUNTLL=1 -DHAVE___BUILTIN_UNREACHABLE=1 -DHAVE_FUNC_ATTRIBUTE_CONST=1 -DHAVE_FUNC_ATTRIBUTE_FLATTEN=1 -DHAVE_FUNC_ATTRIBUTE_FORMAT=1 -DHAVE_FUNC_ATTRIBUTE_MALLOC=1 -DHAVE_FUNC_ATTRIBUTE_PACKED=1 -DHAVE_FUNC_ATTRIBUTE_PURE=1 -DHAVE_FUNC_ATTRIBUTE_RETURNS_NONNULL=1 -DHAVE_FUNC_ATTRIBUTE_UNUSED=1 -DHAVE_FUNC_ATTRIBUTE_VISIBILITY=1 -DHAVE_FUNC_ATTRIBUTE_WARN_UNUSED_RESULT=1 -DHAVE_FUNC_ATTRIBUTE_WEAK=1 -DHAVE_FUNC_ATTRIBUTE_ALIAS=1 -DHAVE_FUNC_ATTRIBUTE_NORETURN=1 -DMAJOR_IN_SYSMACROS=1 -DHAVE_DLADDR=1 -DHAVE_CLOCK_GETTIME=1 -DHAVE_PTHREAD=1 -I. -I../../../src/mesa -D__STDC_CONSTANT_MACROS -D__STDC_FORMAT_MACROS -D__STDC_LIMIT_MACROS -D_GNU_SOURCE -DUSE_SSE41 -DUSE_GCC_ATOMIC_BUILTINS -DNDEBUG -DTEXTURE_FLOAT_ENABLED -DUSE_X86_64_ASM -DHAVE_XLOCALE_H -DHAVE_SYS_SYSCTL_H -DHAVE_STRTOF -DHAVE_MKOSTEMP -DHAVE_TIMESPEC_GET -DHAVE_STRTOD_L -DHAVE_DL_ITERATE_PHDR -DHAVE_POSIX_MEMALIGN -DHAVE_ZLIB -DHAVE_LINUX_FUTEX_H -DHAVE_GALLIUM_EXTRA_HUD=1 -DHAVE_LIBSENSORS=1 -DHAVE_LIBDRM -DGLX_USE_DRM -DGLX_INDIRECT_RENDERING -DGLX_DIRECT_RENDERING -DGLX_USE_TLS -DHAVE_X11_PLATFORM -DHAVE_SURFACELESS_PLATFORM -DHAVE_WAYLAND_PLATFORM -DWL_HIDE_DEPRECATED -DHAVE_DRM_PLATFORM -DHAVE_DRI3 -DENABLE_SHADER_CACHE -DHAVE_MINCORE -DHAVE_ST_VDPAU -DHAVE_LLVM=0x0600 -DMESA_LLVM_VERSION_PATCH=0 -I../../../include -I../../src -I../../../src -I../../src/compiler/glsl -I../../src/compiler/nir -I../../src/mesa -I../../../src/mesa -I../../src/mesa/main -I../../../src/mesa/main -I../../src/mapi -I../../../src/mapi -I../../../src/gallium/include -I../../../src/gallium/auxiliary -I./x86-64 -I../../../src/mesa/x86-64 -Wdate-time -D_FORTIFY_SOURCE=2 -I/usr/lib/llvm-6.0/include -D__STDC_CONSTANT_MACROS -D__STDC_FORMAT_MACROS -D__STDC_LIMIT_MACROS -fvisibility=hidden -Werror=pointer-arith -Werror=vla -g -O2 -fstack-protector-strong -Wformat -Werror=format-security -Wall -Wall -Werror=implicit-function-declaration -Werror=missing-prototypes -Wmissing-prototypes -fno-math-errno -fno-trapping-math -std=c99 -c ../../../src/mesa/state_tracker/st_nir_lower_uniforms_to_ubo.c  -fPIC -DPIC -o state_tracker/.libs/st_nir_lower_uniforms_to_ubo.o
../../../src/mesa/state_tracker/st_nir_lower_uniforms_to_ubo.c:32:17: fatal error: nir.h: No such file or directory
compilation terminated.
Makefile:3041: recipe for target 'state_tracker/st_nir_lower_uniforms_to_ubo.lo' failed
make[6]: *** [state_tracker/st_nir_lower_uniforms_to_ubo.lo] Error 1
make[6]: *** Waiting for unfinished jobs....