ext/gd: pack imageloadfont short-read test in native byte order

imageloadfont_short_read packed the font header with pack('V4', ...)
(little-endian), but imageloadfont() reads the header as native-endian
ints. On big-endian hosts (PPC64 nightly) the byte-swapped values
overflow the INT_MAX guard before the FLIPWORD fallback runs, so the
font is rejected and the test fails. Pack the fields with 'i' to keep
the header valid regardless of host endianness.

Author: iliaal

ext/gd/tests/imageloadfont_short_read.phpt

@@ -7,7 +7,9 @@ gd
 /* A user-space wrapper returns one byte per read, so php_stream_read() hands
  * imageloadfont()'s header loop a short read on every iteration. The header
  * (4 ints) plus a single 1x1 glyph byte form a valid font, which only loads
- * when each short read lands at the correct byte offset. */
+ * when each short read lands at the correct byte offset. imageloadfont() reads
+ * the header as native-endian ints, so pack the fields with 'i' (not 'V') to
+ * keep the font valid on big-endian hosts too. */
 class drip
 {
     public $context;
@@ -16,7 +18,7 @@ class drip
 
     public function stream_open($path, $mode, $options, &$opened): bool
     {
-        $this->data = pack('V4', 1, 32, 1, 1) . "\x00";
+        $this->data = pack('i4', 1, 32, 1, 1) . "\x00";
         return true;
     }