clang -O2  -Wall -Wextra -Werror=implicit-function-declaration signal/sigwait.c -o signal/sigwait -D_GNU_SOURCE -D_BSD_SOURCE -D_ALL_SOURCE -D_DEFAULT_SOURCE  -lm  -lintl
../out/minix/basic/signal/sigwait.o: In function `main':
signal/sigwait.c:(.text+0x35a): undefined reference to `sigwait'
clang: error: linker command failed with exit code 1 (use -v to see invocation)