[CQ] Temporarily make gcc bot experimental due to goma problems

BUG=chromium:626622
NOTRY=true
NOPRESUBMIT=true
TBR=sergiyb@chromium.org

Review-Url: https://codereview.chromium.org/2136443004
Cr-Commit-Position: refs/heads/master@{#37606}

infra/config/cq.cfg

@@ -63,7 +63,10 @@ verifiers {
         name: "v8_linux_dbg_ng_triggered"
         triggered_by: "v8_linux_dbg_ng"
       }
-#      builders { name: "v8_linux_gcc_compile_rel" }
+      builders {
+        name: "v8_linux_gcc_compile_rel"
+        experiment_percentage: 100
+      }
       builders { name: "v8_linux_mipsel_compile_rel" }
       builders { name: "v8_linux_mips64el_compile_rel" }
       builders { name: "v8_linux_nodcheck_rel_ng" }