shims/super/cc: remove leftover usage of llvm-g++-4.2

[cho-m]

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Not sure if there is a situation this needs to be forwarded to another compiler. I think most support forllvm-g* usage was removed in my last PR that dropped the shims

[Bo98]

You'll probably want to remove the remaining *llvm-g* shims too if doing this: https://github.com/Homebrew/brew/tree/master/Library/Homebrew/shims/super. llvm-g++-4.2 in particular still exists.

[MikeMcQuaid]

You'll probably want to remove the remaining *llvm-g* shims too if doing this: master/Library/Homebrew/shims/super. llvm-g++-4.2 in particular still exists.

@Bo98 Good shout. Done.

[MikeMcQuaid]

Thanks @cho-m!