Bundle SDL2 2.30.6

shared-modules only has 2.30.3, I'll send a pr to update but let's
bundle it in the mean time.

SDL2/SDL2-no-libdecor.json

@@ -0,0 +1,22 @@
+{
+  "name": "SDL2",
+  "buildsystem": "autotools",
+  "config-opts": ["--disable-static"],
+  "sources": [
+    {
+      "type": "archive",
+      "url": "https://github.com/libsdl-org/SDL/releases/download/release-2.30.6/SDL2-2.30.6.tar.gz",
+      "sha256": "c6ef64ca18a19d13df6eb22df9aff19fb0db65610a74cc81dae33a82235cacd4"
+    }
+  ],
+  "cleanup": [ "/bin/sdl2-config",
+               "/include",
+               "/lib/libSDL2.la",
+               "/lib/libSDL2main.a",
+               "/lib/libSDL2main.la",
+               "/lib/libSDL2_test.a",
+               "/lib/libSDL2_test.la",
+               "/lib/cmake",
+               "/share/aclocal",
+               "/lib/pkgconfig"]
+}

org.DolphinEmu.dolphin-emu.yml

@@ -65,6 +65,9 @@ modules:
         url: https://github.com/Unrud/xdg-screensaver-shim/archive/0.0.2.tar.gz
         sha256: 0ed2a69fe6ee6cbffd2fe16f85116db737f17fb1e79bfb812d893cf15c728399
 
+  # The kde runtime bundles 2.28.5 but current dolphin versions require 2.30.6
+  - SDL2/SDL2-no-libdecor.json
+
   - name: dolphin-emu
     buildsystem: cmake-ninja
     config-opts: