Remove all usages of "arch" CFLAGS on Mac.

Remove all usages of "arch" CFLAGS on Mac.

Remove all [PPC|PPC64|X86|x86_64] CFLAGS, CXXFLAGS
and OBJECTIVE_CFLAGS. Delete the arch prf files.

32/64 bit arch selection will be made using a different
mechanism in Qt 5. Universal builds are not supported.

Change-Id: I4664f2c31801cec7fb4d240f41c2c5204a109020
Reviewed-by: James Turner <james.turner@kdab.com>
Reviewed-by: Bradley T. Hughes <bradley.hughes@nokia.com>
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>