dry-run mode

[evmar]

Ninja has -n dry run mode. However it's not clear what we should do with respect to things like rsp files.

@jamesr wrote:

The way that I've usually used "-n" is to ask the tool what steps it thinks it should run given the currently available information. In that use case I would consider the rspfile's contents as part of the tool's description of the step that it wants to run and would like access to that information. Another way to factor it would be to have the dry run simply go through the steps it would like to run and have a different query to ask for a fuller description of a particular step or set of steps, including rspfile file contents.