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: Ifea5ed988fad2e0d29271e6e9cbf0e12100b37d9
diff --git a/libs/ui/Android.bp b/libs/ui/Android.bp
index 080336b..8388743 100644
--- a/libs/ui/Android.bp
+++ b/libs/ui/Android.bp
@@ -135,6 +135,7 @@
         "libhardware_headers",
         "libui_headers",
     ],
+    min_sdk_version: "29",
 }
 
 cc_library_headers {
@@ -153,6 +154,7 @@
     export_header_lib_headers: [
         "libnativewindow_headers",
     ],
+    min_sdk_version: "29",
 }
 
 // defaults to enable VALIDATE_REGIONS traces