[WebAssembly] Revert r319488 "Add visibility flag to Wasm symbol flags"

This patch reportedly broke one of LLVM bots (ubuntu-gcc7.1-werror).

See http://lab.llvm.org:8011/builders/ubuntu-gcc7.1-werror/builds/3369 for
details.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@319602 91177308-0d34-0410-b5e6-96231b3b80d8
7 files changed