opencascade-occt: fix compilation on darwin (#365409)

```
FAILED: src/TKV3d/CMakeFiles/TKV3d.dir/__/StdPrs/StdPrs_BRepFont.cxx.o 
/nix/store/raqax5qp65an4jcwj1bzd5lq589ywpg0-clang-wrapper-16.0.6/bin/clang++ -DHAVE_FREETYPE -DHAVE_OPENGL -DHAVE_OPENGL_EXT -DHAVE_TK -DOCC_CO>
/tmp/nix-build-opencascade-occt-7.8.1.drv-0/occt-V7_8_1-bd2a789/src/StdPrs/StdPrs_BRepFont.cxx:460:17: error: cannot initialize a variable of t>
    const char* aTags      = &anOutline->tags[aStartIndex];
                ^            ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
1 error generated.
```

pkgs/by-name/op/opencascade-occt/package.nix

@@ -1,6 +1,7 @@
 { lib
 , stdenv
 , fetchurl
+, fetchpatch
 , cmake
 , ninja
 , tcl
@@ -24,6 +25,15 @@ stdenv.mkDerivation rec {
     hash = "sha256-AGMZqTLLjXbzJFW/RSTsohAGV8sMxlUmdU/Y2oOzkk8=";
   };
 
+  patches = [
+    # fix compilation on darwin against latest version of freetype
+    # https://gitlab.freedesktop.org/freetype/freetype/-/merge_requests/330
+    (fetchpatch {
+      url = "https://github.com/Open-Cascade-SAS/OCCT/commit/7236e83dcc1e7284e66dc61e612154617ef715d6.diff";
+      hash = "sha256-NoC2mE3DG78Y0c9UWonx1vmXoU4g5XxFUT3eVXqLU60=";
+    })
+  ];
+
   nativeBuildInputs = [
     cmake
     ninja