This change moves the build instructions for dependencies to a separate Makefile in deps/. The ARCH environment variable is stored in a .make-arch file in the same directory as the Makefile. The contents of this file is read and compared to the current ARCH, and, on a mismatch triggers rebuilding the entire source tree. When file .make-arch exists and matches with ARCH from the environment, the dependencies are assumed to already be built. The new "clean" target only cleans the Redis source tree, not its dependencies. To clear the dependencies as well, the "distclean" target can be used.