vmbase: Keep vmbase_elf_defaults out of /system

Prevent installing executables intended to run in a VM to /system.

Test: TH
Change-Id: I7d0d8d0ff8ef93a9814a24001a95a8f6d0b94891
diff --git a/vmbase/Android.bp b/vmbase/Android.bp
index 35484ea..fb525b5 100644
--- a/vmbase/Android.bp
+++ b/vmbase/Android.bp
@@ -49,6 +49,7 @@
         "libarm-optimized-routines-mem",
         "libvmbase_entry",
     ],
+    installable: false,
     enabled: false,
     target: {
         android_arm64: {