[cfe-dev] MinGW header search paths (InitHeaderSearch.cpp)

[NAKAMURA Takumi]

I'd rather think lang should have its own libraries and should be
freestanding from GNU toolchain as possible.

For now, for mingw, I suggest two ways;

  1. Support sysroot, by default, "c:/mingw" is assumed.
  2. Add default sysroot as "${clang.exe's dir}/.. , when clang.exe is
installed to ${your_mingw_distro}/bin.

In future, I suggest;

  0. Get rid of gcc.exe driver for linking. Use ld.exe directly.
  1. Provide our mingw. distributed llvm-gcc does.
  2. Provide our compiler_rt and libcxx for mingw.
  3. Provide our linker.

...Takumi