To initialize on Linux:

repo init -u https://github.com/Arc-OS/android.git -b cm-13.0 -g all,-notdefault,-darwin

To initialize on MacOS:

repo init -u https://github.com/Arc-OS/android.git -b cm-13.0 -g all,-notdefault,-linux

Then to sync up:

repo sync --force-sync && repo sync --force-sync

Then to build:

. build/envsetup.sh
lunch cm_$device-userdebug
make -j8 bacon

Example for HTC One XL:

. build/envsetup.sh
lunch cm_evita-userdebug
make -j8 bacon