Always force JDK from prebuilts.
Always force JDK from prebuilts.

CI machines exports JAVA_HOME, so we have to override it.

Test: ./gradlew
Change-Id: I5767d6ec1522bcd85bc7bbe8ccec25ddac93669a

AndroidX/androidx,androidx/androidx,AndroidX/androidx,androidx/androidx,androidx/androidx,androidx/androidx,androidx/androidx,AndroidX/androidx,androidx/androidx,androidx/androidx,AndroidX/androidx,AndroidX/androidx,AndroidX/androidx,AndroidX/androidx,androidx/androidx,AndroidX/androidx,androidx/androidx,AndroidX/androidx,AndroidX/androidx,androidx/androidx