Tweak to flag parsing (#5921)
Tweak to flag parsing (#5921)

-o2/Main.exe should be an invalid flag, not a linker input

MERGED from commit 93299cce9a4f7bc65b8164f779a37ef7f9f7c4a0

ilyasergey/GHC-XAppFix,ilyasergey/GHC-XAppFix,ilyasergey/GHC-XAppFix,ilyasergey/GHC-XAppFix