Use prebuilt aapt if built aapt not exist

Align the rule of using aapt with build system.

Bug: 205720152
Test: tapas MediaProviderTests ;\
      rm $(ANDROID_HOST_OUT)/bin/aapt ;\
      atest MediaProviderTests

Change-Id: Ibeec63881c4724d755f331ee8819f92399552677
3 files changed