Avoid uncondionally colored output when using GCC.
Avoid uncondionally colored output when using GCC.

pmos69/vast,mavam/vast,vast-io/vast,pmos69/vast,vast-io/vast,vast-io/vast,mavam/vast,pmos69/vast,vast-io/vast,vast-io/vast,mavam/vast,pmos69/vast,mavam/vast