Introduce enable_lightweight argument (#7016)

This is a group switch that enables all other lightweight mode switches.

With this, the CI config does not need to be changed for every new
introduced change.

Author: kaidokert

.github/config/chromium_android-arm-lightweight.json

@@ -5,8 +5,7 @@
   ],
   "gn_args": [
     {
-      "disable_xr": true,
-      "disable_bluetooth" : true,
+      "enable_lightweight" : true,
       "target_os": "android",
       "target_cpu": "arm"
     }

.github/config/chromium_linux-lightweight.json

@@ -5,8 +5,7 @@
   ],
   "gn_args": [
     {
-      "disable_xr": true,
-      "disable_bluetooth" : true
+      "enable_lightweight" : true
     }
   ],
   "targets": [

build/config/lightweight.gni

@@ -3,11 +3,15 @@
 # found in the LICENSE file.
 
 # Lightweight build configuration. Only Linux based build is considered.
+declare_args() {
+  enable_lightweight = false
+}
+
 declare_args() {
   # Disable Bluetooth support.
   # Serial which depends on Bluetooth is also excluded from the build.
-  disable_bluetooth = false
+  disable_bluetooth = enable_lightweight
 
   # Disable XR support.
-  disable_xr = false
+  disable_xr = enable_lightweight
 }