[COFF] Fix manifest resource file creation on Windows.

createManifestRes was generating a MemoryBuffer from a TemporaryFile,
keeping the data but removing the file, before passing the file path
to CVTRES.exe, leading to the following error:

  CVTRES : fatal error CVT1101: cannot open 'C:\Users\user\AppData\
  Local\Temp\lld-output-resource-bfee19.res' for reading

With this, we instead create a new TemporaryFile before passing it to cvtres.

Patch from Rudy Pons!

llvm-svn: 287034