Actually use tcmalloc and test for it

Change-Id: I61e47db48fca960b77eafaf4c8bda4b4d9517617
diff --git a/build_tests/tcmalloc.cc b/build_tests/tcmalloc.cc
new file mode 100644
index 0000000..323ee58
--- /dev/null
+++ b/build_tests/tcmalloc.cc
@@ -0,0 +1,3 @@
+#include <stdlib.h>
+
+int main() { malloc(500000); }