Allow android linux builder to use any number of cores.

For the transition from 8 core to 16 core.

Bug: 875708
Change-Id: I73ca7e9062974821a255ecc3147188f139d19cd9
Reviewed-on: https://chromium-review.googlesource.com/1182954
Commit-Queue: Ryan Tseng <hinoka@chromium.org>
Reviewed-by: Takuto Ikuta <tikuta@chromium.org>
Cr-Commit-Position: refs/heads/master@{#584666}

infra/config/global/cr-buildbucket.cfg

@@ -2366,6 +2366,8 @@ buckets {
       auto_builder_dimension: NO
       dimensions: "builder:android-marshmallow-arm64-rel"
       dimensions: "os:Ubuntu-14.04"
+      # TODO(hinoka): Make this 16 core after crbug.com/875708
+      dimensions: "cores:"
       recipe {
         properties: "buildername:android-marshmallow-arm64-rel"
       }