Make SDL3 optional

Gaming shell plugin only builds when SDL3 is present.
KDE CI does not provide SDL3, so the hard REQUIRED was
breaking configure on every pipeline run.

.reuse/dep5

@@ -11,3 +11,7 @@ Files: HACKING.md
 Copyright: Plasma-Mobile contributors
 License: CC-BY-SA-4.0
 
+Files: Nebra.code-workspace
+Copyright: Shift contributors
+License: CC0-1.0
+

CMakeLists.txt

@@ -112,7 +112,7 @@ set_package_properties(PlasmaWaylandProtocols PROPERTIES
 
 find_package(LibKWorkspace CONFIG REQUIRED)
 find_package(Libudev REQUIRED)
-find_package(SDL3 REQUIRED)
+find_package(SDL3)
 
 find_package(KWinDBusInterface)
 set_package_properties(KWinDBusInterface PROPERTIES DESCRIPTION "KWin DBus interface"

components/CMakeLists.txt

@@ -14,4 +14,6 @@ add_subdirectory(wallpaperimageplugin)
 add_subdirectory(dpmsplugin)
 add_subdirectory(screenbrightnessplugin)
 add_subdirectory(raiselockscreenplugin)
-add_subdirectory(gamingshellplugin)
+if(SDL3_FOUND)
+    add_subdirectory(gamingshellplugin)
+endif()

components/gamingshellplugin/CMakeLists.txt

@@ -1,7 +1,6 @@
 # SPDX-FileCopyrightText: 2026 Marco Allegretti
 # SPDX-License-Identifier: EUPL-1.2
 
-find_package(SDL3 REQUIRED)
 find_package(Qt6 REQUIRED COMPONENTS Sql DBus)
 
 ecm_add_qml_module(gamingshellplugin URI org.kde.plasma.private.mobileshell.gamingshellplugin GENERATE_PLUGIN_SOURCE)

icons/sc-places-start-here-shift.svg

@@ -1,3 +1,5 @@
+<!-- SPDX-FileCopyrightText: 2026 Shift contributors -->
+<!-- SPDX-License-Identifier: GPL-2.0-or-later -->
 <svg viewBox="0 0 96 96" xmlns="http://www.w3.org/2000/svg">
   <!-- top-left circle -->
   <circle cx="16" cy="16" r="16" fill="#FBFBFB"/>