rcutorture: Always strip using the cross-compiler

Strip using -s on the compiler command line instead of calling the "strip"
utility as the latter isn't necessarily compatible with the target arch.
Signed-off-by: Willy Tarreau <w@1wt.eu>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>

tools/testing/selftests/rcutorture/bin/mkinitrd.sh

@@ -113,8 +113,7 @@ int main(int argc, int argv[])
 	return 0;
 }
 ___EOF___
-${CROSS_COMPILE}gcc -static -Os -o init init.c
-strip init
+${CROSS_COMPILE}gcc -s -static -Os -o init init.c
 rm init.c
 echo "Done creating a statically linked C-language initrd"