Use unsigned long for prctl argument

uint64_t isn't the right type when running on a 32 bit machine.

BUG=none
TEST=check caps can be dropped on a 32 bit userspace machine like kevin.
minijail0 -u wpa -g wpa -c 3000 -i -t -- /bin/ls

Change-Id: I1ec55dc653fe206a1641f0a971ab2b20c42a2d9c
Signed-off-by: Dylan Reid <dgreid@chromium.org>
diff --git a/system.c b/system.c
index 9373e87..5dbcf54 100644
--- a/system.c
+++ b/system.c
@@ -59,7 +59,7 @@
 	 * need to lock the NO_CAP_AMBIENT_RAISE securebit, since we are already
 	 * configuring the permitted and inheritable set.
 	 */
-	uint64_t securebits =
+	unsigned long securebits =
 	    (SECURE_BITS_NO_AMBIENT | SECURE_LOCKS_NO_AMBIENT) & ~skip_mask;
 	if (!securebits) {
 		return 0;