Note every system has gcc; e.g. OSX "gcc" is actually not gcc, it's some other compiler, clang.
./configure should figure out whether CC should be cc, gcc...
FreeBSD has switched to clang as the default compiler, and does not have gcc (it can be installed, but, well, it's natural to build GAP and the packages with the default compiler, for various reasons)
Note every system has gcc; e.g. OSX "gcc" is actually not gcc, it's some other compiler, clang.
./configure
should figure out whether CC should be cc, gcc...FreeBSD has switched to clang as the default compiler, and does not have gcc (it can be installed, but, well, it's natural to build GAP and the packages with the default compiler, for various reasons)