Add min_sdk_version:R to updatable apexes

APEXes introduced in R need to set min_sdk_version to ensure that they
are built against correct version(30 or R) of stubs (libc/liblog/...).

Bug: 152655956
Test: /vendor/google/build/build_mainline_modules.sh
Change-Id: I4a893c34b09334eea124266287301e479b9e8a59
diff --git a/apex/Android.bp b/apex/Android.bp
index 2df3eea..32e13e3 100644
--- a/apex/Android.bp
+++ b/apex/Android.bp
@@ -33,6 +33,7 @@
     prebuilts: ["com.android.os.statsd.init.rc"],
     name: "com.android.os.statsd-defaults",
     updatable: true,
+    min_sdk_version: "R",
     key: "com.android.os.statsd.key",
     certificate: ":com.android.os.statsd.certificate",
 }