Revert "Revert "Remove libcore Make based droiddoc target.""

This reverts commit Ia80d84e8577ea2beee349e3135ca730a6f7057f8.

Reason for revert:
line 317 in JavaLibrary.mk: include $(LOCAL_PATH)/Docs.mk should not be removed
This fixed the broken build AOSP:master-art:art/tools/buildbot-build.sh --host

Test: Generated old libcore docs:
m out/target/common/docs/libcore-timestamp
Generated new libcore docs:
m core-docs
Compared outputs:
find ~/android/aosp/out/soong/.intermediates/libcore/core-docs/android-common/docs/out \
  -type f -exec md5sum {} \+ | ( cd ~/android/aosp/out/target/common/docs/libcore; md5sum -c --quiet )

Change-Id: I10ae7eff5026a9866acfd188429e5e443bb94240
2 files changed