Update build configs for ANGLE, vulkan-deps, and SwiftShader roll (#669)

Our tests depend on the Xcb and Wayland Vulkan extensions that are provided by SwiftShader. The latest version of SwiftShader now requires you to opt-in to these extensions through build flags.

See: flutter/engine#38650
Part of: flutter/flutter#117932

Author: loic-sharma

build/config/BUILDCONFIG.gn

@@ -297,8 +297,15 @@ is_castos = false
 is_chromecast = false
 is_chromeos_lacros = false
 ozone_platform_headless = false
-ozone_platform_x11 = false
-ozone_platform_wayland = false
+
+# Needed for //third_party/swiftshader and //third_party/angle.
+if (is_linux) {
+  ozone_platform_x11 = true
+  ozone_platform_wayland = true
+} else {
+  ozone_platform_x11 = false
+  ozone_platform_wayland = false
+}
 
 default_library_type = "static_library"
 

build_overrides/wayland.gni

@@ -3,3 +3,6 @@
 # found in the LICENSE file.
 
 # ANGLE expects this to be here.
+
+# Flutter has no wayland third-party dir
+wayland_gn_dir = ""