Audio VTS: Change test utility from dyn to static lib

Bug: 63801053

In order to avoid having to instruct vts-tradefed to push the test
utility library on the target before runing the audio VTS,
duplicating the makefile declaration,
make the library static.

Test: make vts
Test: vts-tradefed run commandAndExit vts --module VtsHalAudioV2_0Target
Change-Id: I7a98b2aaf0e0f6f91a92b7f01df1c630540ad697
Merged-In: I7a98b2aaf0e0f6f91a92b7f01df1c630540ad697
Signed-off-by: Kevin Rocard <krocard@google.com>