Never try to link with `/lib/darwin` (#435)
Never try to link with `/lib/darwin` (#435)

`clang --print-search-dirs` may return `libraries: =` that leads to `/lib/darwin` which may leads to attempt to find `clang_rt.osx` inside this wired path and which fails the build.
alexcrichton/curl-rust,alexcrichton/curl-rust,alexcrichton/curl-rust