Use CMAKE_SYSROOT instead of EMSCRIPTEN_SYSROOT

[xinitrcn1]

No description provided.

[sbc100]

I think the reason we don't do this is that emcc on it own already automatically includes the sysroot.

i.e. you never need to do emcc --sysroot=/path/to/emscripten/sysroot since emcc already knows exactly where its sysroot is. Its not something we expect user to pass.

I think we don't really want cmake to inject and additional --sysroot since it would be redundant.

[sbc100]

If we set the compiler to clang then it would make sense to pass things like --sysroot and --target=wasm32-unknown-emscripten, but when we use the emcc wrapper around clang they are not needed.

[xinitrcn1]

I'm aware emcc itself uses --sysroot..

HOWEVER
many projects use ${CMAKE_SYSROOT} for other miscellany purpouses, most notably:

• pkg search
• pkgconfig
• find package
• checks
• unholy usages of "absolute paths" that depend on ${CMAKE_SYSROOT}

For example shadPS4 uses CMAKE_SYSROOT for checks and stuff, is it bad design? No! As per documentation CMAKE_SYSROOT MUST point to a valid sysroot, otherwise it's not a valid toolchain.