enable PDK to use platform JAVA API

- make platform-java will add necessary Java stuffs from out/target/common/
  to platform.zip
- make platform works as before: no Java libraries
- normal fusion build will pick up the file, and define TARGET_BUILD_PDK_JAVA
  besides TARGET_BUILD_PDK if Java stuffs are included
- For TARGET_BUILD_PDK_JAVA, java.mk does not touch LOCAL_SDK_VERSION, which will lead into
  pulling non-SDK Java APIs

Bug: 6482799

Change-Id: I90b1a0b06dc774150711680a6612f2b97b9eab3f