Revert "Disable BTI for now."

This reverts commit c75994d623.

Reason for revert: BTI shipped in S, and we're going to work on app compat outreach rather than regress this security feature.

Bug: https://issuetracker.google.com/216395195
Bug: https://issuetracker.google.com/233339366
Change-Id: Ic7143d756907ceb574a686258751840ce62c920f
Merged-In: Ic7143d756907ceb574a686258751840ce62c920f

cc/config/arm64_device.go

@@ -33,9 +33,7 @@ var (
 		},
 		"armv8-a-branchprot": []string{
 			"-march=armv8-a",
-			// Disable BTI until drm vendors stop using OS libraries as sources
-			// of gadgets (https://issuetracker.google.com/216395195).
-			"-mbranch-protection=pac-ret",
+			"-mbranch-protection=standard",
 		},
 		"armv8-2a": []string{
 			"-march=armv8.2-a",