prune-packed: Fix uninitialized variable.

The dryrun variable was made local instead of static by the previous
commit, and local variables aren't initialized to zero.
Signed-off-by: NAlexandre Julliard <julliard@winehq.org>
Signed-off-by: NJunio C Hamano <junkio@cox.net>

builtin-prune-packed.c

@@ -56,7 +56,7 @@ void prune_packed_objects(int dryrun)
 int cmd_prune_packed(int argc, const char **argv, const char *prefix)
 {
 	int i;
-	int dryrun;
+	int dryrun = 0;
 
 	for (i = 1; i < argc; i++) {
 		const char *arg = argv[i];