Build: Handle CMAKE_OSX_ARCHITECTURES=(i386|ppc) We don't officially support i386 or PowerPC Mac builds of libjpeg-turbo anymore, but they still work (bearing in mind that PowerPC builds require GCC v4.0 in Xcode 3.2.6, and i386 builds require Xcode 9.x or earlier.) Referring to #495, apparently MacPorts needs this functionality.