[HIP] Relax checks in hip-include-path.hip test case again

The tightened checks from commit 722c39fe did not work
fully for buildbots using symlinks in repo paths. This patch
is not fully reverting 722c39fe, as we still match that
there is a "/lib" somewhere in the path before "/clang/".

So this is once again a bit fragile in case someone would put
their repo in a base directory, for example, named
 "/scratch/lib/foo/clang/llvm-project/". But it is atleast a
bit better than the original checks (avoiding the problem that
commit 722c39fe was solving).