clang -O2  -Wall -Wextra -Werror=implicit-function-declaration spawn/posix_spawnattr_setschedpolicy.c -o spawn/posix_spawnattr_setschedpolicy -D_GNU_SOURCE -D_BSD_SOURCE -D_ALL_SOURCE -D_DEFAULT_SOURCE  -lm  -lintl
spawn/posix_spawnattr_setschedpolicy.c:6:10: fatal error: 'pthread.h' file not found
#include <pthread.h>
         ^
1 error generated.