8aca65 Include <unistd.h> instead of <sys/unistd.h>.

Authored and Committed by Érico Rolim 5 years ago
    Include <unistd.h> instead of <sys/unistd.h>.
    
    On glibc systems, the <sys/unistd.h> header simply redirects to
    <unistd.h>, while on musl systems this header doesn't exist. Therefore,
    it makes more sense to include <unistd.h> directly.