luci: fix recipe configs for chromium.clang:ToTiOS{,Device}.

TBR=hinoka@chromium.org

Bug: 889399,861396,885799
Change-Id: I7cb770cbe0d4b94f3de501c1e8bc55e37ccd77ce
Reviewed-on: https://chromium-review.googlesource.com/1246283Reviewed-by: John Budorick <jbudorick@chromium.org>
Commit-Queue: John Budorick <jbudorick@chromium.org>
Cr-Commit-Position: refs/heads/master@{#594329}

infra/config/global/cr-buildbucket.cfg

@@ -440,10 +440,16 @@ builder_mixins {
   }
 }
 
+builder_mixins {
+  name: "ios"
+  mixins: "mac"
+  mixins: "xcode-caches"
+}
+
 builder_mixins {
   name: "ios-ci"
+  mixins: "ios"
   mixins: "mac-ci"
-  mixins: "xcode-caches"
   # ios bots may run both on Mac Minis with cores:4 and VMs with cores:8.
   dimensions: "cores:"
   recipe {
@@ -453,8 +459,8 @@ builder_mixins {
 
 builder_mixins {
   name: "ios-try"
+  mixins: "ios"
   mixins: "mac-try"
-  mixins: "xcode-caches"
   recipe {
     name: "ios/try"
   }
@@ -1657,12 +1663,18 @@ buckets {
     builders {
       name: "ToTiOS"
       mixins: "clang-ci"
-      mixins: "mac"
+      mixins: "ios"
+      recipe {
+        name: "ios/unified_builder_tester"
+      }
     }
     builders {
       name: "ToTiOSDevice"
       mixins: "clang-ci"
-      mixins: "mac"
+      mixins: "ios"
+      recipe {
+        name: "ios/unified_builder_tester"
+      }
     }
     builders {
       name: "UBSanVptr Linux"