Don't enable SSE for wasm compilation #7650
Description
In #7130 we had disabled setting SSE for WASM compilation which helped in removing a bunch of warnings for WASM compilation.
We discovered that this PR causes some performance regressions (in effect it actually disabled SSE for x86 compilation as well) and did some investigation in rust-lang/cargo#11114. For now we have reverted the above PR. This issue is to track the work to disable setting SSE for WASM in a way that does not cause a performance regression.