Add BUILD_BROKEN_DONT_CHECK_SYSTEMSDK

https://android-review.git.corp.google.com/q/topic:limit_systemsdk
introduced a new check for preventing the use of system SDKs above 34
from Java modules in the vendor partition.

As this may break some unprepared targets, introduce
BUILD_BROKEN_DONT_CHECK_SYSTEMSDK as a temporary escape hatch.

This flag will be deleted eventually.

Bug: 314011075
Test: Add BUILD_BROKEN_DONT_CHECK_SYSTEMSDK := true to BoardConfig.mk
Change-Id: Id7901f85c221bc03fa1c15ef15dbec14b783a79a
diff --git a/android/sdk_version.go b/android/sdk_version.go
index 9c84a27..73568af 100644
--- a/android/sdk_version.go
+++ b/android/sdk_version.go
@@ -306,7 +306,7 @@
 func (s SdkSpec) ValidateSystemSdk(ctx EarlyModuleContext) bool {
 	// Do some early checks. This check is currently only for Java modules. And our only concern
 	// is the use of "system" SDKs.
-	if !isJava(ctx.Module()) || s.Kind != SdkSystem {
+	if !isJava(ctx.Module()) || s.Kind != SdkSystem || ctx.DeviceConfig().BuildBrokenDontCheckSystemSdk() {
 		return true
 	}