native frameworks: 64-bit compile issues

- Fix format (print/scanf)
- Suppress unused argument warning messages (bonus)

Change-Id: I05c7724d2aba6da1e82a86000e11f3a8fef4e728
diff --git a/cmds/flatland/GLHelper.cpp b/cmds/flatland/GLHelper.cpp
index 42694b3..05d082b 100644
--- a/cmds/flatland/GLHelper.cpp
+++ b/cmds/flatland/GLHelper.cpp
@@ -332,7 +332,7 @@
 
 static void printShaderSource(const char* const* src) {
     for (size_t i = 0; i < MAX_SHADER_LINES && src[i] != NULL; i++) {
-        fprintf(stderr, "%3d: %s\n", i+1, src[i]);
+        fprintf(stderr, "%3zu: %s\n", i+1, src[i]);
     }
 }