Don't pass -lc to Emscripten, it breaks

[hoodmane]

Before this patch,

echo "fn main(){}" > a.rs
rustc -Copt-level=z a.rs -o a.js --target=wasm32-unknown-emscripten

fails with:

error: undefined symbol: _emscripten_memcpy_js (referenced by root reference (e.g. compiled C/C++ code))
warning: To disable errors for undefined symbols use `-sERROR_ON_UNDEFINED_SYMBOLS=0`
warning: __emscripten_memcpy_js may need to be added to EXPORTED_FUNCTIONS if it arrives from a system library
Error: Aborting compilation due to previous errors
emcc: error: '/home/rchatham/Documents/programming/emsdk/node/18.20.3_64bit/bin/node /home/rchatham/Documents/programming/emsdk/upstream/emscripten/src/compiler.mjs /tmp/tmpogw1glcz.json' failed (returned 1)          

There are quite a few other sets of linker arguments that trigger this problem, but this is the shortest. Applying this patch to rust-libc and overriding the version of libc used in library/Crates.toml to use the patched version, I have verified locally that the crash goes away.

See:
emscripten-core/emscripten#22742
emscripten-core/emscripten#16680
rust-lang/rust#98155
rust-lang/rust#98303
rust-lang/rust#131885

cc @workingjubilee @sbc100

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[hoodmane]

Thanks @tgross35! Can this get a backport? It's blocking for rust-lang/rust#131736, so it would be convenient to have a released version with this change that I can use sometime soon if possible.

[tgross35]

Yes this will be backported (it already has the nomination). Usually I do backports and a release once every few weeks, the next one will be pretty soon.