build: aux: Fix link type checking for AUX builds

AUX build environent is volatile and is only instantiated in
a context of AUX-aware module.
link-type checking is happening outside such context, and
is not able to correctly determine AUX build dependencies.

1. Save enough of context in LINK_TYPE variable;
   Use AUX-<variant-name> instead of AUX
2. Load correct set of AUX meta build vars before
   building link_type rules

Bug: 62060489
Test: make auxiliary

build no longer tries to access "/STATIC_LIBRARIES" path

Change-Id: I9764d4a0740da1c55a6f8429398872fc4362942c