[patch] Use ld.lld2 as a argv[0] alias

[Rafael Espíndola via llvm-commits]

On 1 October 2015 at 18:53, Rui Ueyama <ruiu at google.com> wrote:
> I'd use StringRef::endswith_lower instead of path::extension (why do we have
> that function btw?).

Some uses are silly (like the one I was about to add), but there seems
to be some valid ones:

* We want to do something else with the extension, like creating a
second file with the same extension as the same one.
* We want to check against multiple extensions and use a StringSwitch for it.

Cheers,
Rafael