[clang] [clang][LoongArch] Add OHOS target (PR #127555)

[Lu Weining via cfe-commits]

SixWeining wrote:

> > Could you add some tests in ohos.c with the `--sysroot` option specified?
> 
> Could I confirm what the test targeting the `--sysroot` option is for? Is it also intended to test the `page-size`?

I mean the purpose is to check whether clang driver passes correct options to cc1 or lld. For example, the `ld-musl-loongarch64.so.1`, `crti.o`, `crt1.o`, etc.

https://github.com/llvm/llvm-project/pull/127555