Use updatable sysprop to for enabling APEX mgmt

This should prevent unnecessary communication with apexd on devices that
don't support APEX package management.

Bug: 130623080
Test: CTS tests on marlin (no APEX support) and cuttlefish
Change-Id: Ic5fdb088aa1530b3c5aecbd5abd3d794a364c775
diff --git a/Android.bp b/Android.bp
index 0fcc0d5..abf95a8 100644
--- a/Android.bp
+++ b/Android.bp
@@ -687,6 +687,7 @@
         "core/java/com/android/server/DropboxLogTags.logtags",
         "core/java/org/chromium/arc/EventLogTags.logtags",
 
+        ":apex-properties",
         ":platform-properties",
 
         ":framework-statslog-gen",
@@ -1834,4 +1835,4 @@
     name: "framework-aidl-mappings",
     srcs: [":framework-defaults"],
     output: "framework-aidl-mappings.txt"
-}
\ No newline at end of file
+}