[lldb/tests] Correctly configure the lldb dotest arguments

Summary:
When the generator used for CMake is a multi-configuration generator (such as VS), the arguments passed to dotest are not currently configured correctly. There are a couple of issues:
1) The per-configuration files are all generated for the same configuration since the for loop overwrites the properties
2) Not all of the parameters are configured in the lit cfg, so they end up with %(build_mode)s as configuration and they point to non-existent paths

Reviewers: JDevlieghere

Reviewed By: JDevlieghere

Subscribers: mgorny, lldb-commits, asmith

Tags: #lldb

Differential Revision: https://reviews.llvm.org/D74093