Infra: add android_clang_dbg_recipe LUCI builder to buildbucket cfg.

Bug: 731967
Change-Id: I94e8f9d5342293f8ac9e6e2af4ee0c33f082282c
Reviewed-on: https://chromium-review.googlesource.com/1045445Reviewed-by: Andrii Shyshkalov <tandrii@chromium.org>
Commit-Queue: Erik Staab <estaab@chromium.org>
Cr-Commit-Position: refs/heads/master@{#556275}

infra/config/global/cr-buildbucket.cfg

@@ -1254,6 +1254,11 @@ buckets {
       name: "android_arm64_dbg_recipe"
       dimensions: "os:Ubuntu-14.04"
     }
+    builders {
+      mixins: "android-try"
+      name: "android_clang_dbg_recipe"
+      dimensions: "os:Ubuntu-14.04"
+    }
     builders {
       mixins: "android-try"
       name: "android_compile_dbg"