dex2oat: Fix repeatedly preparing dex files for oat file

to reduce compilation time when compiling dex files individually.

Test:
    enable DumpTiming first
    adb shell setprop pm.dexopt.install quicken
    adb install xxx.apk
    #check dex2oat timing in logcat(SetDexFiles repeatedly)

Change-Id: Ia9973f03540a51af2c49d996b5ccb8ab3e009e5a
Signed-off-by: wulonghua <wulonghua@xiaomi.com>
3 files changed