When cross-compiling on macOS, like building on ARM64 to target x86_64 [1], `make install` would fail with `winebuild: cannot find the 'ar' tool`. `winebuild` was looking for `x86_64-apple-darwin-ar`, but macOS does not install prefixed tools. As a last step before failing in `find_tool()`, search for the un-prefixed tool name.
[1]: with a `configure` invocation like: `../configure --enable-archs=i386,x86_64 --host=x86_64-apple-darwin CC="clang -arch x86_64"`
-- v2: winebuild: As a last resort, search for tools un-prefixed using clang. winebuild: Refactor find_tool().