cc -pthread  -Wall -Wextra -Werror=implicit-function-declaration unistd/getgroups.c -o unistd/getgroups -D_GNU_SOURCE -D_BSD_SOURCE -D_ALL_SOURCE -D_DEFAULT_SOURCE -lm -lpthread -lrt -lintl -liconv
unistd/getgroups.c: In function ‘main’:
unistd/getgroups.c:10:23: error: implicit declaration of function ‘getgroups’ [-Wimplicit-function-declaration]
   10 |         int ngroups = getgroups(0, NULL);
      |                       ^~~~~~~~~