Guard dbus component and config with assert(use_dbus)

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 9e56b770fd97987a21fc56737764c95fe77c198d..c6867670026ad69f562e91b0f13ac3fc18b89113 100644
--- a/build/config/linux/BUILD.gn
+++ b/build/config/linux/BUILD.gn
@@ -3,6 +3,7 @@
 # found in the LICENSE file.
 
 import("//build/config/linux/pkg_config.gni")
+import("//build/config/ui.gni")
 
 group("linux") {
   visibility = [ "//:optimize_gn_gen" ]
@@ -83,11 +84,13 @@ config("libresolv") {
   libs = [ "resolv" ]
 }
 
-pkg_config("glib") {
-  packages = [
-    "glib-2.0",
-    "gmodule-2.0",
-    "gobject-2.0",
-    "gthread-2.0",
-  ]
+if (use_glib) {
+  pkg_config("glib") {
+    packages = [
+      "glib-2.0",
+      "gmodule-2.0",
+      "gobject-2.0",
+      "gthread-2.0",
+    ]
+  }
 }