build: check if m4 macro exists
build: check if m4 macro exists

frida/libunwind,unkadoug/libunwind,rantala/libunwind,yuyichao/libunwind,djwatson/libunwind,vtjnash/libunwind,libunwind/libunwind,libunwind/libunwind,yuyichao/libunwind,vtjnash/libunwind,libunwind/libunwind,rantala/libunwind,djwatson/libunwind,frida/libunwind,djwatson/libunwind,rantala/libunwind,frida/libunwind,unkadoug/libunwind,unkadoug/libunwind,yuyichao/libunwind,vtjnash/libunwind