Auto merge of #2963 - devnexen:recvmsg_linux_fix, r=JohnTitor
Auto merge of #2963 - devnexen:recvmsg_linux_fix, r=JohnTitor

linux fixes recvmmsg flags type for musl/emscripten.

closes #2945

rust-lang/libc,rust-lang/libc,rust-lang/libc