QSS-M, a port of ID Software's original Quake, evolved from Quake 1.09 to Fitzquake, Quakespasm, Quakespasm Spiked, and now Quakespasm Spiked Multiplayer. NetQuake competitive multiplayer clients began with ProQuake, progressed to Qrack or Mark V, and arrived at QSS-M, thanks to voluntary contributions
Recent linux gcc (ubuntu container on chromebook) seems to default this flag to off, as well. Adding flag to linux makefile seems to do the trick.