More ports that break without /usr/bin/gcc

[Christian Weisgerber]

I removed /usr/bin/gcc and ran a test build on amd64.  These ports
broke because they have calls to "gcc" hardcoded somewhere:

lang/compcert
lang/nim
math/fftw3
misc/rocrail

-- 
Christian "naddy" Weisgerber                          na...@mips.inka.de