run ninja -j80 for mac goma staging.

in chromium.goma, mac goma staging runs on 4 cores mac vm,
which runs ninja -40 by default.
it would take ~2 hours for full builds (cache misses cases).

let's run ninja -j80 to mitigate such cases.

Bug: 901699, b/115585306
Change-Id: I1bc637c29cd47c339af1148ed5f7e36dc857021d
Reviewed-on: https://chromium-review.googlesource.com/c/1317220Reviewed-by: Takuto Ikuta <tikuta@chromium.org>
Reviewed-by: Shinya Kawanaka <shinyak@chromium.org>
Commit-Queue: Fumitoshi Ukai <ukai@chromium.org>
Cr-Commit-Position: refs/heads/master@{#605274}

infra/config/global/cr-buildbucket.cfg

@@ -116,6 +116,18 @@ builder_mixins {
   }
 }
 
+# This is for 4 cores mac. -j40 is too small, especially for clobber builder.
+builder_mixins {
+  name: "goma-j80"
+  recipe {
+    properties_j: <<END
+    $build/goma: {
+      "jobs": 80
+    }
+    END
+  }
+}
+
 builder_mixins {
   name: "android"
   dimensions: "os:Android"
@@ -2490,6 +2502,7 @@ buckets {
       dimensions: "os:Mac-10.13"
       dimensions: "cores:4"
       mixins: "goma-ci"
+      mixins: "goma-j80"
     }
     builders {
       name: "Chromium Android ARM 32-bit Goma RBE Staging"
@@ -2506,6 +2519,7 @@ buckets {
       dimensions: "os:Mac-10.13"
       dimensions: "cores:4"
       mixins: "goma-ci"
+      mixins: "goma-j80"
     }
     builders {
       name: "Chromium Linux Goma RBE Staging (dbg) (clobber)"
@@ -2517,6 +2531,7 @@ buckets {
       dimensions: "os:Mac-10.13"
       dimensions: "cores:4"
       mixins: "goma-ci"
+      mixins: "goma-j80"
     }
     builders {
       name: "Chromium Linux Goma Staging"