unit-test: Compile source files into object libraries
unit-test: Compile source files into object libraries

This improves compilation time as we now only compile source files
once and reuse the object files.

Change-Id: Ie75fec64490d8843688d23229a37312fbcc4e3a8
Reviewed-by: Scott Parlane <85029adc3fa41ef14594a57826619713bfe95f25@alliedtelesis.co.nz>
Signed-off-by: Matt Bennett <e3d8681cec70d3da741935b3385821001b249adc@alliedtelesis.co.nz>

ATL-NZ/buildsyspp,alliedtelesis/buildsyspp