Put prebuilt emulator path after host output

So that built emulator is used instead of prebuilt one when
BUILD_EMULATOR=true.

Change-Id: I67dfbfc2c3bf9bf051e56de425caa07b08d4b2e4
Increase system image size to 650M for generic_arm64

Change-Id: I7969ec54dc4225bbe36651c4d9c6a09de1eb89f4
Merge "Increase system image size to 650M for generic_arm64"
Merge "Put prebuilt emulator path after host output"
auto-merger: merge in from aosp/master