Pipeline interfaces should be well specified #28

We have a pipeline that looks a bit like this

• CMake
  • accepts a complicated family of options
  • builds some dependencies
  • creates a build.ninja file to tell ninja how to build the tools
• ninja
  • builds binaries of tools
  • puts them somewhere
• run-all.ps1
  • runs the tools to calculate benchmarks
  • the timing information is written to specially-named files
• plot_graphs.py
  • looks for the specially-named timing files
  • generates graphs
  • puts the graphs somewhere

It would be great to have a specification of each step of the pipeline. What are the arguments it accepts? Where does it have to be run?[1] What are its outputs? Where are files placed and what is their specification?

[1] Ideally any tool should be able to be run in any directory. It shouldn't decide where to read or write files based on its current working directory.