graphite2: fix build with gcc15

- add patch from fedora, that adds missing `#include <stdint.h>`

Fixes build failure with gcc15:
```
/build/graphite2-1.3.14/tests/featuremap/featuremaptest.cpp: In function 'void testFeatTable(const T&, const std::string&)':
/build/graphite2-1.3.14/tests/featuremap/featuremaptest.cpp:310:14: error: 'uint16_t' was not declared in this scope [-Wtemplate-body]
  310 |         for (uint16_t j = 0; j < table.m_defs[i].m_numFeatSettings; j++)
      |              ^~~~~~~~
/build/graphite2-1.3.14/tests/featuremap/featuremaptest.cpp:310:14: note: 'uint16_t' is defined in header '<cstdint>'; this is probably fixable by adding '#include <cstdint>'
/build/graphite2-1.3.14/tests/featuremap/featuremaptest.cpp:310:30: error: 'j' was not declared in this scope [-Wtemplate-body]
  310 |         for (uint16_t j = 0; j < table.m_defs[i].m_numFeatSettings; j++)
      |                              ^
```

pkgs/development/libraries/silgraphite/graphite2.nix

@@ -2,6 +2,7 @@
   lib,
   stdenv,
   llvmPackages,
+  fetchpatch,
   fetchurl,
   pkg-config,
   freetype,
@@ -39,7 +40,14 @@ stdenv.mkDerivation (finalAttrs: {
     }
   );
 
-  patches = lib.optionals stdenv.hostPlatform.isDarwin [ ./macosx.patch ];
+  patches = [
+    # Fix build with gcc15
+    (fetchpatch {
+      url = "https://src.fedoraproject.org/rpms/graphite2/raw/deba28323b0a3b7a3dcfd06df1efc2195b102ed7/f/graphite2-1.3.14-gcc15.patch";
+      hash = "sha256-vkkGkHkcsj1mD3OHCHLWWgpcmFDv8leC4YQm+TsbIUw=";
+    })
+  ]
+  ++ lib.optionals stdenv.hostPlatform.isDarwin [ ./macosx.patch ];
   postPatch = ''
     # disable broken 'nametabletest' test, fails on gcc-13:
     #   https://github.com/silnrsi/graphite/pull/74