Revert "Enable -D_FORTIFY_SOURCE=3 globally by default."

Revert submission 3391212-_FORTIFY_SOURCE=3

Reason for revert: DroidMonitor: Potential culprit for http://b/383164857 - verifying through ABTD before revert submission. This is part of the standard investigation process, and does not mean your CL will be reverted.

Reverted changes: /q/submissionid:3391212-_FORTIFY_SOURCE%3D3

Change-Id: I37fef362894c04e8c409c6df22eee0e3a7e8d99f
diff --git a/cc/config/global.go b/cc/config/global.go
index 61f48c4..b19682d 100644
--- a/cc/config/global.go
+++ b/cc/config/global.go
@@ -166,7 +166,7 @@
 		"-funwind-tables",
 		"-fstack-protector-strong",
 		"-Wa,--noexecstack",
-		"-D_FORTIFY_SOURCE=3",
+		"-D_FORTIFY_SOURCE=2",
 
 		"-Wstrict-aliasing=2",