Followup to r1560558, unbreak builds with installed APR/APR-util builds.

* build/generator/gen_win_dependencies.py
   (GenDependenciesBase._find_apr,
    GenDependenciesBase._find_apr_util_and_expat): Need both tests since the
     debug_dll_dir will be None with binary installs.


git-svn-id: https://svn.apache.org/repos/asf/subversion/trunk@1560560 13f79535-47bb-0310-9956-ffa450edef68