Copy libandroidio.so from the Runtime APEX to /system in ART testing.

Add libandroidio.so to the list of Runtime APEX libraries copied in
/system for testing by the standalone-apex-files Make phony target.

Test: ART chroot-based on-device testing using the master-art branch
Bug: 121117762
Change-Id: I06bde7c7db9e2a7e130f3cad932101d152176f8a
diff --git a/Android.mk b/Android.mk
index 9222a19..5105617 100644
--- a/Android.mk
+++ b/Android.mk
@@ -528,6 +528,8 @@
   lib64/libdexfile_external.so \
   lib/libnativeloader.so \
   lib64/libnativeloader.so \
+  lib/libandroidio.so \
+  lib64/libandroidio.so \
 
 .PHONY: standalone-apex-files
 standalone-apex-files: libc.bootstrap libdl.bootstrap libm.bootstrap linker com.android.runtime.debug