cmake: make the GRIM option available for all compilers.
cmake: make the GRIM option available for all compilers.

Tested with gcc 4.2.1, clang 3.0 and pcc 1.0 on FreeBSD 9.0.

Signed-off-by: Cyril Roelandt <73ab1f8ebf7a7cfe55f85ed775611eefab6987ae@gmail.com>

MichielPater/dfc,Rolinh/dfc