Revert "Revert "Revert "Switch external cvtres.exe for llvm's own resource library."""

This reverts commit ae21ee0b6cacbc1efaf4d42502e71da2f0eb45c3.

The initial revert was done in order to prevent ongoing errors on
chromium bots such as CrWinClangLLD.  However, this was done haphazardly
and I didn't realize there were test and compilation failures, so this
revert was reverted.  Now that those have been fixed, we can revert the
revert of the revert.

llvm-svn: 307227