build/ci: specifying gcc base image
build/ci: specifying gcc base image

JayKickliter/liquid-dsp,jgaeddert/liquid-dsp,jgaeddert/liquid-dsp,jgaeddert/liquid-dsp,JayKickliter/liquid-dsp,JayKickliter/liquid-dsp,wangning223/liquid-dsp,JayKickliter/liquid-dsp,wangning223/liquid-dsp,JayKickliter/liquid-dsp,jgaeddert/liquid-dsp,wangning223/liquid-dsp,wangning223/liquid-dsp,jgaeddert/liquid-dsp,wangning223/liquid-dsp