Add unit test for apexer_with_DCLA_preprocessing.

Add unit test for the DCLA apexer wrapper. It uses a simple example
apex, expand it, add some artificial lib files, and then invoke the DCLA
apexer wrapper. The resulting apex should have these artificial lib
files properly placed like

/lib(64)?/[lib name]/[lib hash]/[lib name]

BUG: b/241096765
TETS: added unit test
Change-Id: I420ce56ef5d1d73598c2862978db10fb2df8fd5a
4 files changed