[clang] Reapply "[Driver][OHOS] Fix lld link issue for OHOS (#118192)" (PR #120159)

[Peng Huang via cfe-commits]

phuang wrote:

> We need a test to clang/test/Driver/ohos.c similar to linux-ld.c clang_rt.crtbegin.o.
> 
> You can add UNSUPPORTED: system-windows to ohos.c so that we don't need backslashes.

[ohos.c](https://github.com/llvm/llvm-project/blob/main/clang/test/Driver/ohos.c#L25
) already has many tests for it. This PR changes behavior of function [OHOS::getCompilerRT()](https://github.com/llvm/llvm-project/pull/120159/files#diff-763eb55ff16745f240d46c78f988f7a2010f61d2ae2550260b3dcd65dd9ba1c7L341). It will search extra folders for compiler rt builtin libraries. But in tests, OHOS::getCompilerRT()'s return value will not be changed, becasue those extra folders don't have those requested builtin files. It will just returns the default library file path.

https://github.com/llvm/llvm-project/pull/120159