Move explicit GC after we are done initalizing all classes.

Previously we had the GC happen for each dex file, this added a
few seconds of time on boot.oat creation.

Bug: 16853450

(cherry picked from commit 093ef212b7db4c17ed62df5cac0c1ac3a24e691d)

Change-Id: Ia469838eff1550c175c3465a478d8081023601bd
1 file changed