[PATCH] lld: handling of -flavor / -core command line switches

[Oleg Ranevskyy]

>>! In D5384#18, @ruiu wrote:
> So I'm OK with your patch if there's no objection from other LLD engineers.

Thank you Rui.
I've clang-formatted the patch and added a simple test for it.

I am using --help in the test to keep it as simple as possible. 
In practice, the flavor's need to be the 1st argument may result in more unevident and confusing errors. E.g., when building Boost lld was receiving the command line similar to "ld -v -z relro -flavor gnu...". Without the patch lld output was "lld: cannot find file relro", as UniversalDriver was skipping the "-v -z" part.

http://reviews.llvm.org/D5384