Fix compilation warning when building for arm64

When building for arm64, NSInteger is a 64-bit value. Recommendations
are to either use "%ld" and cast the value to long or to use "%zd".
This patch uses "%zd" that work on both armv7 and arm64 as it avoid
doing a cast.

DELTA=1  (0 added, 0 deleted, 1 changed)

1 files changed, 1 insertions, 1 deletions

diff --git a/iPhone/GTMUIImage+Resize.m b/iPhone/GTMUIImage+Resize.m
index 49b82c8..c22515e 100644
--- a/iPhone/GTMUIImage+Resize.m
+++ b/iPhone/GTMUIImage+Resize.m
@@ -152,7 +152,7 @@ GTM_INLINE CGSize swapWidthAndHeight(CGSize size) {
       break;
 
     default:
-      _GTMDevAssert(false, @"Invalid orientation %d", orientation);
+      _GTMDevAssert(false, @"Invalid orientation %zd", orientation);
       return nil;
   }