On macOS, without a 3rd party package manager installed (e.g. Homebrew), libraries/osx/build-osx-libs.sh fails with the following error:
checking for NETTLE... configure: error: *** *** Libnettle 3.1 was not found. ERROR: GnuTLS build failed
This is the result of GnuTLS using pkg-config to check for nettle, hogweed, and other dependencies. Since there is no built-in option for overriding this behavior, this patch simply removes those error cases, using our custom configure flags instead.