Make the resolver unit test statically link the resolver library.

The unit test for the library must link the library statically.
Otherwise, it's testing the version of the library currently
running on the device, which doesn't make sense.

Test: builds, boots
Test: system/netd/tests/runtests.sh resolv_unit
Change-Id: I95c22298013c8d577693246b68f6e011dc7da45e