clang -O2  -Wall -Wextra -Werror -Wno-error=deprecated -Wno-error=deprecated-declarations unistd/_POSIX_REALTIME_SIGNALS.c -o unistd/_POSIX_REALTIME_SIGNALS -D_POSIX_C_SOURCE=202405L  -lm  -lintl
unistd/_POSIX_REALTIME_SIGNALS.c:3:2: error: "_POSIX_REALTIME_SIGNALS is not defined"
#error "_POSIX_REALTIME_SIGNALS is not defined"
 ^
1 error generated.