qt6.qtsvg: add mingw support

Part of a larger effort to add mingw support to qtmultimedia.

pkgs/development/libraries/qt-6/modules/qtsvg.nix

@@ -5,11 +5,20 @@
 , libmng
 , zlib
 , pkg-config
+, lib
+, stdenv
 }:
 
 qtModule {
   pname = "qtsvg";
   propagatedBuildInputs = [ qtbase ];
-  buildInputs = [ libwebp jasper libmng zlib ];
+  buildInputs = [
+    libwebp
+  ] ++ lib.optionals (stdenv.buildPlatform.canExecute stdenv.hostPlatform) [
+    jasper
+  ] ++ [
+    libmng
+    zlib
+  ];
   nativeBuildInputs = [ pkg-config ];
 }