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.
* SOURCE_URI: switch to https and to tar.bz2.
* Sort BUILD_PREREQUIRES.
* Drop unneeded call to libtoolize.
* Remove empty $libDir on secondary arch builds.