The gcc wrapper can't handle trailing backslashes

The gcc wrapper will choke on trailing backslashes in arguments, like -Iinclude\ or -Llibs\. realgcc handles them fine. It seems to insert as spurious quote or terminating a quote too early.

Error message:

.\test-ghc.c:1:20: fatal error: test-inc"/header.h: Invalid argument
compilation terminated.

Found here: https://github.com/idris-lang/Idris-dev/issues/3801