Using the 10.2.6 release zip (ftp://ftp.freedesktop.org/pub/mesa/10.2.6/MesaLib-10.2.6.zip) with the VS2012 compiler.

scons invocation:
LLVM=c:/llvm /c/Python27/python /c/Python27/Scripts/scons.py build=release machine=x86 platform=windows gles=yes llvm=yes MSVC_VERSION=11.0

This line:

unsigned texcoord_size = 2 + (src_rb->Depth > 1 ? 1 : 0);

in setup_glsl_blit_framebuffer() results in a syntax error:

src\mesa\drivers\common\meta_blit.c(331) : error C2143: syntax error : missing ';' before 'type'

Moving the declaration to the top of the function fixes the error:

{
   unsigned texcoord_size = 0;

   /* target = GL_TEXTURE_RECTANGLE is not supported in GLES 3.0 */
   assert(_mesa_is_desktop_gl(ctx) || target == GL_TEXTURE_2D);

   texcoord_size = 2 + (src_rb->Depth > 1 ? 1 : 0);
   ...