[gnutls] - if gnutls is there don't compile OSXGNUReplacements as they are duped in gnutls already
[depends] - fix target config site script. It wants to set LD_LIBRARY_PATH to the deps dir not to the native buildtools. Found when trying to get ffmpeg gnutls to work. On osx ffmpeg tried to pull in libz from native dir instead of system toolchain because ld_library_path was set wrong
[xcode] - link against gnutls and related deps