Add 'lo-prio' tag to temp blocklist.

This is a temporary measure to allow these APIs to be identified by
downstream tooling. Before S is finished, these APIs will be moved
to the max-target-R list anyway.

Adding the lo-prio flag should have no semantic impact on these APIs
but does allow them to be distinguished from the regular blocklist
APIs.

Test: m
Bug: 174455522
Change-Id: I031dcecbdef34a4f93a0fec1a92d95f769918486
diff --git a/java/hiddenapi_singleton.go b/java/hiddenapi_singleton.go
index e57f323..8f0e09c 100644
--- a/java/hiddenapi_singleton.go
+++ b/java/hiddenapi_singleton.go
@@ -259,7 +259,7 @@
 		FlagWithInput("--blocked ",
 			android.PathForSource(ctx, "frameworks/base/config/hiddenapi-force-blocked.txt")).
 		FlagWithInput("--blocked ",
-			android.PathForSource(ctx, "frameworks/base/config/hiddenapi-temp-blocklist.txt")).
+			android.PathForSource(ctx, "frameworks/base/config/hiddenapi-temp-blocklist.txt")).FlagWithArg("--tag ", "lo-prio").
 		FlagWithInput("--unsupported ", android.PathForSource(
 			ctx, "frameworks/base/config/hiddenapi-unsupported-packages.txt")).Flag("--packages ").
 		FlagWithOutput("--output ", tempPath)