Old gcc/libc fails to build (no MAP_FIXED_NOREPLACE)

[theofficialgman]

https://github.com/Pi-Apps-Coders/box64-debs/actions/runs/35086722908/job/104763157130#step:5:2931

/github/workspace/box64/src/wrapped/wrappedlibc.c:3832:49: error: 'MAP_FIXED_NOREPLACE' undeclared (first use in this function)
             !(flags & (MAP_SHARED | MAP_FIXED | MAP_FIXED_NOREPLACE)) &&
                                                 ^~~~~~~~~~~~~~~~~~~
/github/workspace/box64/src/wrapped/wrappedlibc.c:3832:49: note: each undeclared identifier is reported only once for each function it appears in

[ptitSeb]

Ok. I have added some workaround.

Btw, you should check the new BOX64_ONDEMAND_STEAMUI=1 settings (add it in a [*] section of ~/.box64 for easy use), it can help running steam+games on machine with low memory.