x86_64 is used as a baseline: the "x86_64" entry, whatever status it has,
is transformed into "all", and then the other entries in ARCHITECTURES
either dropped or rearranged appropriately.
* Add commandSuffix and relativeCommandBinDir.
* Update the sed command in PATCH(), mostly s/@prefix@/$(PREFIX)/,
and also make "make install" check if librubberband-jni.so exists
before trying to install it. (We need javac to build it.)