Always link gperftools to support CPU profiling

Change-Id: I7b455f7f713f231d71c3e31f1ec00bcfcfac14f3
diff --git a/third_party/gperftools/BUILD b/third_party/gperftools/BUILD
index 65d9b1b..8807e6c 100644
--- a/third_party/gperftools/BUILD
+++ b/third_party/gperftools/BUILD
@@ -137,6 +137,7 @@
     '//third_party/empty_config_h',
   ],
   copts = common_copts,
+  alwayslink = True,
   nocopts = '-std=gnu\+\+1y',
 )