luci: add linux-tcmalloc-rel to chromium.fyi console.

Tbr: martiniss@chromium.org,thakis@chromium.org
Bug: 868024
Change-Id: I4a21b8b2c42fa46752bea47c04b0ea501fc13981
Reviewed-on: https://chromium-review.googlesource.com/c/1345073Reviewed-by: John Budorick <jbudorick@chromium.org>
Commit-Queue: John Budorick <jbudorick@chromium.org>
Cr-Commit-Position: refs/heads/master@{#609862}

infra/config/global/luci-milo.cfg

@@ -2878,6 +2878,10 @@ consoles {
     name: "buildbucket/luci.chromium.ci/VR Linux"
     category: "linux"
   }
+  builders {
+    name: "buildbucket/luci.chromium.ci/linux-tcmalloc-rel"
+    category: "linux"
+  }
   builders {
     name: "buildbot/chromium.fyi/Mojo Android"
     name: "buildbucket/luci.chromium.ci/Mojo Android"