Allow disabling DroidDoc build.

Change-Id: Ia842827a46b107bcef0d176deb0ab651e04bfa04
envsetup: export ANDROID_BUILD_TOP earlier

Change-Id: Ia3497f61f4e9aaeeb793cecd3b4f488f0a48181a
CM on Emulator [ARM]

* set TARGET_NO_KERNEL to false
* Add recovery.fstab
* Add goldfish target

Change-Id: If5104d6e949706f79c673ae26060870f86e18c62