Re-land: Resurrect Aura Linux accessibility.

build/config/linux/BUILD.gn

Index: build/config/linux/BUILD.gn
diff --git a/build/config/linux/BUILD.gn b/build/config/linux/BUILD.gn
index 202fd731897a89f29addd715f1c1150b751dde3c..3d65937dd42dd6cee74f4e79c9a56ec77b978446 100644
--- a/build/config/linux/BUILD.gn
+++ b/build/config/linux/BUILD.gn
@@ -35,6 +35,25 @@ config("sdk") {
   }
 }
 
+pkg_config("atk") {
+  packages = [ "atk" ]
+  atk_lib_dir = exec_script(pkg_config_script,
+                            [
+                              "--libdir",
+                              "atk",
+                            ],
+                            "string")
+  defines = [ "ATK_LIB_DIR=\"$atk_lib_dir\"" ]
+}
+
+# gn orders flags on a target before flags from configs. The default config
+# adds -Wall, and these flags have to be after -Wall -- so they need to come
+# from a config and can't be on the target directly.
+config("atk_warnings") {
+  # glib uses the pre-c++11 typedef-as-static_assert hack.
+  cflags = [ "-Wno-unused-local-typedef" ]
+}
+
 config("fontconfig") {
   libs = [ "fontconfig" ]
 }