Incidentally gcc is not required for sourcing the rc files. You can simply ignore the error message or, if you can't ignore it, replace the file $FSLDIR/etc/fslconf/fslmachtype.sh with
http://www.fmrib.ox.ac.uk/~duncan/fslmachtype.sh
This patch will be made to the shipping fsl soon.
Cheers, Dave
Dave Flitney, IT Manager
Oxford Centre for Functional MRI of the Brain