Enable -Wfortify-source

This reverts commit 885f2eec3c96b6e0ffe06229032366c3b8e862e5.

Reason for revert: Fixed the error reported in post-submit

Change-Id: I152494403e6d6937413d0e5d2637d426c2f54009
diff --git a/cc/config/global.go b/cc/config/global.go
index 62a4765..d2faff2 100644
--- a/cc/config/global.go
+++ b/cc/config/global.go
@@ -376,8 +376,6 @@
 		"-Wno-unqualified-std-cast-call",
 		"-Wno-array-parameter",
 		"-Wno-gnu-offsetof-extensions",
-		// TODO: Enable this warning http://b/315245071
-		"-Wno-fortify-source",
 	}
 
 	llvmNextExtraCommonGlobalCflags = []string{