[PECOFF] Better error handling for /manifest.

git-svn-id: https://llvm.org/svn/llvm-project/lld/trunk@193143 91177308-0d34-0410-b5e6-96231b3b80d8
[PECOFF] Add /manifestuac command line option.

This option is used for the manifest file too.

git-svn-id: https://llvm.org/svn/llvm-project/lld/trunk@193145 91177308-0d34-0410-b5e6-96231b3b80d8