Use grep instead of sed because on Solaris sed doesn't copy null bytes and

Use grep instead of sed because on Solaris sed doesn't copy null bytes and
it needs to in order for the bug in MacOSX archives to be tested correctly.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@18269 91177308-0d34-0410-b5e6-96231b3b80d8