[PECOFF] Ignore /disallowlib.

msvcrt.lib contains "/disallowlib" command line option in its .drectve section.
I couldn't spot any documentation for the option. Ignore it for now so that we
can link the library without error.

git-svn-id: https://llvm.org/svn/llvm-project/lld/trunk@194114 91177308-0d34-0410-b5e6-96231b3b80d8