Fix linking issue (missing wayland-client library) (flutter#21408)

As fl_renderer_wayland.cc uses directly some of the wayland-client
related functions it should also add this library as a dependency.

Author: dwrobel

shell/platform/linux/BUILD.gn

@@ -80,7 +80,10 @@ source_set("flutter_linux_sources") {
              "fl_standard_message_codec_private.h",
            ]
 
-  configs += [ "//flutter/shell/platform/linux/config:gtk" ]
+  configs += [
+    "//flutter/shell/platform/linux/config:gtk",
+    "//flutter/shell/platform/linux/config:wayland-client",
+  ]
 
   sources = [
     "egl_utils.cc",

shell/platform/linux/config/BUILD.gn

@@ -22,3 +22,7 @@ pkg_config("egl") {
 pkg_config("wayland-egl") {
   packages = [ "wayland-egl" ]
 }
+
+pkg_config("wayland-client") {
+  packages = [ "wayland-client" ]
+}