Here's how I'm building crosswords for Android.

First, cd into the directory xwords4/android/XWords4. Everything
happens there.

IF (and it's a big if) you have all the necessary tools installed (the
Android SDK and NDK, apache ant, and probably other stuff I've
forgotten), two commands will build it, the first a one-time deal and
the second repeated every time you made a change.

The build process requires a file called local.properties that must be
generated locally.  Generate it before your first build by running

# ../scripts/setup_local_props.sh 

Then build using this command:

# ant debug 

Or, if you have a device or emulator attached (listed by 'adb
devices'), try

# ant debug install

Making a release build requires that you've set up your keys.  (I did
this too long ago to remember how but the info's easy to find).  Once
that's done, just tether your device and type

# ant release install