infra/config: Use RBE_PROD backend for CrOS builder

This is currently set to use the RBE backend via the recipe config.
Specify it in the builder config instead.

Bug: 1022800
Change-Id: I27955c8012682847987c65daec9d2de64898369c
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1906460
Auto-Submit: Simon Que <sque@chromium.org>
Reviewed-by: Yoshisato Yanagisawa <yyanagisawa@google.com>
Reviewed-by: Takuto Ikuta <tikuta@chromium.org>
Commit-Queue: Takuto Ikuta <tikuta@chromium.org>
Cr-Commit-Position: refs/heads/master@{#714373}

infra/config/buckets/ci/goma.star

@@ -480,6 +480,7 @@ goma_builder(
 goma_builder(
     name = 'chromeos-amd64-generic-rel (Goma RBE FYI)',
     builderless = True,
+    goma_backend = goma.backend.RBE_PROD,
     goma_enable_ats = True,
 )
 

infra/config/generated/cr-buildbucket.cfg

@@ -7533,7 +7533,7 @@ buckets: <
         name: "chromium"
         cipd_package: "infra/recipe_bundles/chromium.googlesource.com/chromium/tools/build"
         cipd_version: "refs/heads/master"
-        properties_j: "$build/goma:{\"enable_ats\":true}"
+        properties_j: "$build/goma:{\"enable_ats\":true,\"rpc_extra_params\":\"?prod\",\"server_host\":\"goma.chromium.org\"}"
         properties_j: "$kitchen:{\"devshell\":true,\"git_auth\":true}"
         properties_j: "mastername:\"chromium.goma\""
       >