mkswap: tolerate ENOTSUP when failing to relabel

It might be that the underlying filesystem just doesn't support SELinux
labeling. This fixes creating swap on vfat live media:

  # livecd-iso-to-disk.sh --msdos --swap-size-mb 666 ...

Signed-off-by: Lubomir Rintel <lkundrak@v3.sk>

disk-utils/mkswap.c

@@ -522,7 +522,7 @@ int main(int argc, char **argv)
 		context_string = context_str(newcontext);
 
 		if (strcmp(context_string, oldcontext)!=0) {
-			if (fsetfilecon(ctl.fd, context_string))
+			if (fsetfilecon(ctl.fd, context_string) && errno != ENOTSUP)
 				err(EXIT_FAILURE, _("unable to relabel %s to %s"),
 						ctl.devname, context_string);
 		}