Set min_sdk_version for updatable mainline modules

Modules contributing mainline modules (APK/APEX) should set
min_sdk_version as well as apex_available.

For now setting min_sdk_version doesn't change build outputs.
But build-time checks will be added soon.

Bug: 145796956
Bug: 150999716
Test: m
Merged-In: Ifaecb49a47a1f43edea3ea06e1cf704a177d1044
Change-Id: Ifaecb49a47a1f43edea3ea06e1cf704a177d1044
(cherry picked from commit 33aa294e96f13906f596e427b96652fe80cf199b)
diff --git a/Tethering/apex/Android.bp b/Tethering/apex/Android.bp
index 20ccd2a..67097a7 100644
--- a/Tethering/apex/Android.bp
+++ b/Tethering/apex/Android.bp
@@ -17,7 +17,7 @@
 apex {
     name: "com.android.tethering",
     updatable: true,
-    min_sdk_version: "R",
+    min_sdk_version: "current",
     java_libs: ["framework-tethering"],
     apps: ["Tethering"],
     manifest: "manifest.json",