configure_debug: Add label warning that CPU JIT needs to be disabled for gdbstub to work

src/citra_qt/configuration/configure_debug.ui

@@ -22,6 +22,13 @@
         <string>GDB</string>
        </property>
        <layout class="QVBoxLayout" name="verticalLayout_2">
+        <item>
+         <widget class="QLabel">
+          <property name="text">
+           <string>The GDB Stub only works correctly when the CPU JIT is off.</string>
+          </property>
+         </widget>
+        </item>
         <item>
          <layout class="QHBoxLayout" name="horizontalLayout_3">
           <item>