Fix nondeterminstic iteration of vndk modules map

Sort the list of libraries when iterating over the vndk modules
map to avoid a non-deterministic output file.

Test: m nothing && mv out/soong/build.ninja /tmp && m nothing && diff -u out/soong/build.ninja /tmp/build.ninja
Change-Id: I889736715dab491bb7e69f3499ab1a5e2c876171