Provides better visibility into what the build is currently doing.
Motivated by slow node.js downloads making the build appear stuck.
You can test this out by running ./tools/install-n2 then building
normally. Please report any problems, and 'cargo uninstall n2' to get
back to the old behaviour. It works on Windows, but prints a new line
each second instead of redrawing the same area.
A couple of changes were required for compatibility:
- n2 doesn't resolve $variable names inside other variables, so the
resolution needs to be done by our build generator.
- Our inputs and outputs in build.ninja need to be listed in a deterministic
order to avoid unwanted rebuilds. I've made a few other tweaks so the
build file should now be fully-deterministic.
