[PATCH] Makefile.common: add scratch build targets

[Till Maas]

Aloas,

the attached patch adds support for scratch builds to Makefile.common:

scratch-build     Request scratch build of "fcgi-2_4_0-2_fc8" for dist-f8
scratch-build-<archs>   Request scratch build of "fcgi-2_4_0-2_fc8" for 
dist-f8 and archs <archs>
                examples:  make scratch-build-i386,ppc64
                           make scratch-build-x86_64

Regards,
Till