In particular, cmake seems to be crapping out. I have cmake installed and can build other stuff with it so I'm not sure what's up.
> emsdk install clang-incoming-64bit emscripten-incoming-64bit sdk-incoming-64bit
Installing tool 'clang-incoming-64bit'..
Cloning into 'D:/devtools/Emscripten/clang/fastcomp\src'...
remote: Counting objects: 1225067, done.
remote: Compressing objects: 100% (3/3), done.
remote: Total 1225067 (delta 0), reused 0 (delta 0), pack-reused 1225064
Receiving objects: 100% (1225067/1225067), 259.89 MiB | 1.57 MiB/s, done.
Resolving deltas: 100% (1008950/1008950), done.
Checking connectivity... done.
Checking out files: 100% (19961/19961), done.
Fetching latest changes to the branch 'incoming' for 'D:/devtools/Emscripten/clang/fastcomp\src'...
Already up-to-date.
Successfully updated and checked out branch 'incoming' on repository 'D:/devtools/Emscripten/clang/fastcomp\src'
Current repository version: "Fri, 21 Oct 2016 00:02:52 +0300 c08775cd9e861d17f95083d248e0e79ff66646f3"
Cloning into 'D:/devtools/Emscripten/clang/fastcomp\src\tools/clang'...
remote: Counting objects: 592596, done.
remote: Compressing objects: 100% (3/3), done.
remote: Total 592596 (delta 0), reused 0 (delta 0), pack-reused 592593
Receiving objects: 100% (592596/592596), 123.70 MiB | 1.43 MiB/s, done.
Resolving deltas: 100% (501570/501570), done.
Checking connectivity... done.
Checking out files: 100% (11528/11528), done.
Fetching latest changes to the branch 'incoming' for 'D:/devtools/Emscripten/clang/fastcomp\src\tools/clang'...
Already up-to-date.
Successfully updated and checked out branch 'incoming' on repository 'D:/devtools/Emscripten/clang/fastcomp\src\tools/clang'
Current repository version: "Fri, 21 Oct 2016 00:03:16 +0300 82589d2fa5e8f3af2fea7274111ba90609c03496"
Running CMake: ['cmake', '-G', 'Visual Studio 12 Win64', '-DCMAKE_BUILD_TYPE=RelWithDebInfo', '-DPYTHON_EXECUTABLE=D:\\devtools\\Emscripten\\python\\2.7.5.3_64b
it\\python.exe', '-DLLVM_TARGETS_TO_BUILD=X86;JSBackend', '-DLLVM_INCLUDE_EXAMPLES=OFF', '-DCLANG_INCLUDE_EXAMPLES=OFF', '-DLLVM_INCLUDE_TESTS=OFF', '-DCLANG_IN
CLUDE_TESTS=OFF', 'D:/devtools/Emscripten/clang/fastcomp\\src']
-- The C compiler identification is unknown
-- The CXX compiler identification is unknown
-- The ASM compiler identification is GNU
-- Found assembler: D:/mingw-w64/i686-5.3.0-posix-dwarf-rt_v4-rev0/mingw32/bin/gcc.exe
CMake Error at CMakeLists.txt:48 (project):
No CMAKE_C_COMPILER could be found.