Don't desugar static java libraries

Static java libraires are designed to be included in another
java library.  If desugar runs on the static java library,
the resulting jar will contain the desugared lambda classes.
When the static jar is included into another java library
and desugar runs again, it desugars the static java library
classes again, producing the same desugared lambda classes
and colliding in the final jar.

Test: m -j ANDROID_COMPILE_WITH_JACK=false
Change-Id: I0508b2cc9c56dbbd4ac0aba44fb99ea2a27715e0