[COFF] Fix .rsrc sections with differing permissions

GNU windres, and MS cvtres (unless the /readonly option is passed)
produce read-write .rsrc sections, when creating resource object files.
This caused the sections to not be added to the precreated RsrcSec,
and therefore not be added to the data directory.

Differential Revision: https://reviews.llvm.org/D63837

llvm-svn: 364660