Two updates are proposed for clang scripts:
An optional parameter is added to run_tool.py called (tool-param) that is directly passed to the tool that is run.
An optional parameter is added to generate_win_compdb.py to specify the build directory. Its default value is out/Debug so that it won't change the previous behavior.

BUG=670072

Review-Url: https://codereview.chromium.org/2542563002
Cr-Commit-Position: refs/heads/master@{#435532}