Fail to build LDC2 on Windows 7 X64

[Zhouxuan]

I tried building LDC2 on windows according to 
http://wiki.dlang.org/Building_and_hacking_LDC_on_Windows_using_MSVC, 
but failed while building phobos-ldc.vcxproj.

The error is:
...
...
Generating std/file.obj
  Unknown frame setup opcode!
  UNREACHABLE executed at 
D:\ldcenv\llvm\lib\Target\X86\X86MCInstLower.cpp:707!
  Stack dump:
0.        Running pass 'X86 Assembly / Object Emitter' on 
function '@_D3std4file6getcwdFZAya'