build: including stdlib.h to enable exit with strict errors
build: including stdlib.h to enable exit with strict errors

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