[Mac/GN] Properly set the install_name and rpath for shared_library targets and their consumers. BUG=621932 R=cwallez@chromium.org Change-Id: I10b0fd5a668d74b7062747002bc48ef0e0a6df9c Reviewed-on: https://chromium-review.googlesource.com/354302 Reviewed-by: Corentin Wallez <cwallez@chromium.org> Commit-Queue: Corentin Wallez <cwallez@chromium.org>