Restore "Default to zero-initialization instead of pattern."

This reverts commit 39fa1882ac7285f60c9b45e99f13a8b54e41b73a.

Reason for revert: Original test was broken (go/oag/1311137), so restoring correct build/soong change.

Bug: http://b/156464649
Test: atest CtsNNAPITestCases:TensorRankConstraint

Change-Id: Id87b6a265a3541e95bcf2d68097738929e88e8b2
diff --git a/cc/config/global.go b/cc/config/global.go
index 4e51ae9..5f28c87 100644
--- a/cc/config/global.go
+++ b/cc/config/global.go
@@ -162,7 +162,7 @@
 
 		// http://b/131390872
 		// Automatically initialize any uninitialized stack variables.
-		// Prefer zero-init if both options are set.
+		// Prefer zero-init if multiple options are set.
 		if ctx.Config().IsEnvTrue("AUTO_ZERO_INITIALIZE") {
 			flags = append(flags, "-ftrivial-auto-var-init=zero -enable-trivial-auto-var-init-zero-knowing-it-will-be-removed-from-clang")
 		} else if ctx.Config().IsEnvTrue("AUTO_PATTERN_INITIALIZE") {
@@ -170,8 +170,8 @@
 		} else if ctx.Config().IsEnvTrue("AUTO_UNINITIALIZE") {
 			flags = append(flags, "-ftrivial-auto-var-init=uninitialized")
 		} else {
-			// Default to pattern initialization.
-			flags = append(flags, "-ftrivial-auto-var-init=pattern")
+			// Default to zero initialization.
+			flags = append(flags, "-ftrivial-auto-var-init=zero -enable-trivial-auto-var-init-zero-knowing-it-will-be-removed-from-clang")
 		}
 
 		return strings.Join(flags, " ")