Add a temporary requirement for Mac bots to have XCode.

BUG=chromium:884015

Change-Id: Iee2373b23ab5534165b36c40600cae86545ee3d9
Reviewed-on: https://dawn-review.googlesource.com/1544
Reviewed-by: Kai Ninomiya <kainino@chromium.org>
Reviewed-by: Stephen White <senorblanco@chromium.org>
diff --git a/infra/config/global/cr-buildbucket.cfg b/infra/config/global/cr-buildbucket.cfg
index 1c78612..611ae0c 100644
--- a/infra/config/global/cr-buildbucket.cfg
+++ b/infra/config/global/cr-buildbucket.cfg
@@ -124,11 +124,15 @@
       name: "mac-dbg"
       dimensions: "os:Mac-10.13"
       mixins: "debug"
+      # Require XCode temporarily to avoid https://crbug.com/884015
+      dimensions: "xcode_version:9.3"
     }
     builders {
       name: "mac-rel"
       dimensions: "os:Mac-10.13"
       mixins: "release"
+      # Require XCode temporarily to avoid https://crbug.com/884015
+      dimensions: "xcode_version:9.3"
     }
 
     # Linux: test combinations of {clang,msvc}x{release,debug}x{x86,x64}
@@ -250,12 +254,16 @@
       name: "mac-dbg"
       dimensions: "os:Mac-10.13"
       mixins: "debug"
+      # Require XCode temporarily to avoid https://crbug.com/884015
+      dimensions: "xcode_version:9.3"
     }
     # Actually on the CQ
     builders {
       name: "mac-rel"
       dimensions: "os:Mac-10.13"
       mixins: "release"
+      # Require XCode temporarily to avoid https://crbug.com/884015
+      dimensions: "xcode_version:9.3"
     }
 
     # Actually on the CQ