Set min_sdk_version to be part of 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: 152655956
Test: m
Merged-In: I831bf9f87b520110b5460915e2d7c5814c1dba49
Change-Id: I831bf9f87b520110b5460915e2d7c5814c1dba49
(cherry picked from commit a727a250d76565202d5d57681acbab94e88f13ca)
diff --git a/Android.bp b/Android.bp
index a9c478b..de2c7b9 100644
--- a/Android.bp
+++ b/Android.bp
@@ -24,6 +24,8 @@
     },
     // The minimum sdk version required by users of this module.
     sdk_version: "minimum",
+    // As part of mainline modules(APEX), it should support at least 29(Q)
+    min_sdk_version: "29",
 }
 
 cc_library_headers {
@@ -36,6 +38,8 @@
         },
     },
     sdk_version: "current",
+    // As part of mainline modules(APEX), it should support at least 29(Q)
+    min_sdk_version: "29",
 }
 
 cc_library_headers {