Do not build lsdump for APEX variants

This commit stops building lsdump files for APEX variants since APEX
variants are local to APEX modules themselves.

Bug: 121986692
Test: make findlsdumps  # compare $ANDROID_PRODUCT_OUT/lsdump_paths.txt
Change-Id: I37fcd152d0d84d235a354ea53e53e808dd71464a