Add linux-gcc-rel to the explicit chromium.linux waterfall too.

The bot is now correctly displayed in the main console, but it
doesn't show up in the chromium.linux console or in the tryserver
builder list. This should fix that.

Bug: chromium:776284
Change-Id: Iea27c9f65510f8452dbaadb277e854bf30585b89
Reviewed-on: https://chromium-review.googlesource.com/997332Reviewed-by: Ryan Tseng <hinoka@chromium.org>
Commit-Queue: Patrik Höglund <phoglund@chromium.org>
Cr-Commit-Position: refs/heads/master@{#549128}

infra/config/global/luci-milo-dev.cfg

@@ -856,6 +856,11 @@ consoles: {
     category: "release"
     short_name: "bld"
   }
+  builders: {
+    name: "buildbot/chromium.linux/linux-gcc-rel"
+    category: "release"
+    short_name: "gcc"
+  }
   builders: {
     name: "buildbot/chromium.linux/Linux Tests"
     name: "buildbucket/luci.chromium.ci/Linux Tests"
@@ -3781,6 +3786,9 @@ consoles: {
   builders: {
     name: "buildbot/tryserver.chromium.linux/linux_chromium_ubsan_rel_ng"
   }
+  builders: {
+    name: "buildbot/tryserver.chromium.linux/linux-gcc-rel"
+  }
   builders: {
     name: "buildbot/tryserver.chromium.linux/layout_test_leak_detection"
   }

infra/config/global/luci-milo.cfg

@@ -891,6 +891,11 @@ consoles: {
     category: "release"
     short_name: "bld"
   }
+  builders: {
+    name: "buildbot/chromium.linux/linux-gcc-rel"
+    category: "release"
+    short_name: "gcc"
+  }
   builders: {
     name: "buildbucket/luci.chromium.ci/linux64-jumbo-rel"
     category: "jumbo"
@@ -4373,6 +4378,9 @@ consoles: {
   builders: {
     name: "buildbot/tryserver.chromium.linux/linux_chromium_ubsan_rel_ng"
   }
+  builders: {
+    name: "buildbot/tryserver.chromium.linux/linux-gcc-rel"
+  }
   builders: {
     name: "buildbot/tryserver.chromium.linux/layout_test_leak_detection"
   }