Return errno from F_OFD_SETLKW failure path in fcntl.

Author: jtstogel

libc/src/__support/OSUtil/linux/fcntl.cpp

@@ -66,7 +66,7 @@ ErrorOr<int> fcntl(int fd, int cmd, void *arg) {
         LIBC_NAMESPACE::syscall_impl<int>(FCNTL_SYSCALL_ID, fd, cmd, &flk64);
     // On failure, return
     if (ret < 0)
-      return Error(-1);
+      return Error(-ret);
     // Check for overflow, i.e. the offsets are not the same when cast
     // to off_t from off64_t.
     if (static_cast<off_t>(flk64.l_len) != flk64.l_len ||