Remove unsupported libc++ modules from module.modulemap

[monrandria]

Trying to "import std" (using C++ 20xx modules) results in a bunch of errors, as the module.modulemap includes several unsupported std APIs (mostly related to synchronization). Simply commenting out the unsupported APIs from the module.modulemap is sufficient to fix the errors. Would maybe be nice to do this by default.

[sbc100]

IIUC the two module maps in wasi-sdk are built directly from llvm and not maintained by us:

./lib/clang/10.0.0/include/module.modulemap
./share/wasi-sysroot/include/c++/v1/module.modulemap

I'm not sure how they get built but I would imagine any bugs there are upstream llvm bugs. If you have specific ideas about how to fix them that would be most welcome.

They might be fixed simply by the llvm 15 upgrade which is due any day now (since it was just released).