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
Change-Id: Ida890adfe6dfac79267fc0e18b63d2330266438c
diff --git a/libsystem/Android.bp b/libsystem/Android.bp
index ff886fd..db61669 100644
--- a/libsystem/Android.bp
+++ b/libsystem/Android.bp
@@ -8,6 +8,7 @@
         "//apex_available:platform",
         "//apex_available:anyapex",
     ],
+    min_sdk_version: "apex_inherit",
     export_include_dirs: ["include"],
 
     target: {