Running a short android-build - LAVA CI cycle

Hello,

When testing Android-build to LAVA integration (not the builds themselves), it's sometime beneficial to have quick build cycle which build something (just anything) without error and submits that to LAVA, to avoid ~1hr wait for the normal build.

One way to achieve that is to add "MAKE_TARGETS=userdatatarball" to the build config, as exemplified with https://android-build.linaro.org/builds/~pfalcon/lava-test/ . Build then takes ~12mins, lower-bounded by repo checkout time.

Of course, that won't produce complete Android build, so validation in LAVA will fail.