Stage third-party tool output in a temp directory for checking

[widdowquinn]

pdp makes many calls to third-party tools. With the addition of the --recovery option, after a stall/server kick, the output of these tools can be trusted without checking. This might cause future problems if the output was incomplete.

One way to avoid these problems would be to stage third-party output in a temp directory. For instance:

• Build command line as usual, but replace output directory with a temp directory
• Run the third-party command, and monitor the return code
• If return code is zero, move the tool's output into the actual output directory
  • Else: raise an error and log