rename use_x11 to ozone_platform_x11

Ozone is default now in Chromium and non-Ozone/X11 (aka use_x11) is
deprecated. During the transition period use_x11 == ozone_platform_x11.

Bug: chromium:1096425
Change-Id: Ie3643360ec6607796533054bdedf8e2bb8e7e749
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/231650
Commit-Queue: Mirko Bonadei <mbonadei@webrtc.org>
Reviewed-by: Mirko Bonadei <mbonadei@webrtc.org>
Cr-Commit-Position: refs/heads/main@{#35040}
diff --git a/webrtc.gni b/webrtc.gni
index a32e7bf..3d8c538 100644
--- a/webrtc.gni
+++ b/webrtc.gni
@@ -8,9 +8,9 @@
 import("//build/config/arm.gni")
 import("//build/config/features.gni")
 import("//build/config/mips.gni")
+import("//build/config/ozone.gni")
 import("//build/config/sanitizers/sanitizers.gni")
 import("//build/config/sysroot.gni")
-import("//build/config/ui.gni")
 import("//build_overrides/build.gni")
 
 if (!build_with_chromium && is_component_build) {
@@ -124,7 +124,7 @@
   rtc_build_tools = true
 
   # Set this to false to skip building code that requires X11.
-  rtc_use_x11 = use_x11
+  rtc_use_x11 = ozone_platform_x11
 
   # Set this to use PipeWire on the Wayland display server.
   # By default it's only enabled on desktop Linux (excludes ChromeOS) and