Defer to clang for `--hash-style`.

We fixed the clang driver to "do the right thing" based on target api level years ago, but these manual workarounds predate that (or were copy & pasted from places that predated that). We don't need them any more.

See https://github.com/android/ndk/issues/2005 for more detail.

Change-Id: I995741b8606e389e8de8272f1cc532624516245a