The PathScale compiler silently accepts unknown options that start in
more than one '-':
$ touch foo.c
$ pathcc -c foo.c --junk
$ echo $?
0
$ pathcc -c foo.c ---junk
$ echo $?
0
$ pathcc -c foo.c -junk
pathcc ERROR parsing -junk: unknown flag
$ echo $?
2
We teach the TryCompile to pass a bogus flag with only one '-' instead
of three '-'s for this compiler.
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