[mach-o]: remove dylib install-name test with a.out

Unfortunately, the creation of (the default) output file, a.out races with all
the other tests in this directory. When the wrong one is read by macho-dump,
the test fails.
clang-modernize: Instantiate llvm::Registry<TransformFactory>.
clang-tidy: Instantiate llvm::Registry<clang::tidy::ClangTidyModule>.
[asan] Fix unused variable warning.