bug#19733: disfunctional gcc binary when GCJ or gfortran is installed

Hi Guix, installing the gcj or the gfortran package, my profile's /bin directory gets a gcc link. If I use Guix as a package manager on top of another system that has a working installation of the GNU C compiler and my profile bin path has preference to all other items in PATH, then I end up with

bug#19708: Bowtie fails to build

Fixed in 241e12219. Thanks to Ricardo and Andreas for sorting this out! Mark