Fix error handling for LibC.clock_gettime(CLOCK_MONOTONIC) calls (#…

…15309)

POSIX `clock_gettime` returns 0 on success and -1 on error. See https://man7.org/linux/man-pages/man3/clock_gettime.3.html#RETURN_VALUE

src/crystal/system/unix/time.cr

@@ -39,9 +39,8 @@ module Crystal::System::Time
       nanoseconds = total_nanoseconds.remainder(NANOSECONDS_PER_SECOND)
       {seconds.to_i64, nanoseconds.to_i32}
     {% else %}
-      if LibC.clock_gettime(LibC::CLOCK_MONOTONIC, out tp) == 1
-        raise RuntimeError.from_errno("clock_gettime(CLOCK_MONOTONIC)")
-      end
+      ret = LibC.clock_gettime(LibC::CLOCK_MONOTONIC, out tp)
+      raise RuntimeError.from_errno("clock_gettime(CLOCK_MONOTONIC)") unless ret == 0
       {tp.tv_sec.to_i64, tp.tv_nsec.to_i32}
     {% end %}
   end