Work around a strange bug in Qt5 that causes melonDS to crash on launch

...but only with LTO enabled
...but only on some UNIX systems
...but only with some additional build options except when it breaks
   without any as well

src/frontend/qt_sdl/CMakeLists.txt

@@ -222,4 +222,10 @@ if (UNIX AND NOT APPLE)
 
     install(FILES ${CMAKE_SOURCE_DIR}/res/net.kuribo64.melonDS.desktop DESTINATION ${CMAKE_INSTALL_PREFIX}/share/applications)
     install(TARGETS melonDS BUNDLE DESTINATION ${CMAKE_BINARY_DIR} RUNTIME DESTINATION ${CMAKE_INSTALL_PREFIX}/bin)
+
+    if (NOT USE_QT6)
+        set_target_properties(melonDS PROPERTIES
+            INTERPROCEDURAL_OPTIMIZATION OFF
+            INTERPROCEDURAL_OPTIMIZATION_RELEASE OFF)
+    endif()
 endif()