Revert "[WebAssemby] Support main functions with alternate signatures."

This reverts commit 959e37e669b0c3cfad4cb9f1f7c9261ce9f5e9ae.
That commit doesn't handle the case where main is declared rather than defined,
in particular the even-more special case where main is a prototypeless
declaration (which is of course the one actually used by musl currently).

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@320121 91177308-0d34-0410-b5e6-96231b3b80d8
2 files changed