Minimal device tree for building TWRP using CM12.1 sources.
Initializing repo
repo init -u git://github.com/CyanogenMod/android.git -b cm-12.1
repo sync
Or download the compressed CM12.1 source from here: http://forum.xda-developers.com/android/software/sources-android-sources-highly-t3231109
Cloning device tree
git clone https://github.com/kirito96/android_device_alcatel_5017O 5017O
Make a folder in /devices called alcatel. Copy the 5017O device tree in that /alcatel folder.
Open the terminal and type sh cm12b to run the build script.
Enjoy.