Cmake is producing a clean build everytime

[takameyer]

cmakebuild.js is hardcoded to 'rebuild', which cleans all build artifacts beforhand. This is problematic for incremental builds in CI. This hardcodes it to 'build' instead

[vweevers]

I don't use cmake myself so would like to hear from cmake users. I have no objections (except that it's asymmetrical with node-gyp where we do use rebuild).

[vweevers]

@takameyer To remove the risk of breakage and speed up landing this PR, perhaps the behavior should be opt-in. Via a new command line option, like --no-clean or --no-rebuild. WDYT?

[takameyer]

@vweevers that seems fair. I would prefer a --clean flag, but I think for consistency a --no-clean flag would be appropriate. Are there other places int this tool where this could be implemented?

[vweevers]

The new option can be added to defaults here:

prebuild/rc.js

Lines 8 to 10 in 7c08103

	var rc = require('rc')('prebuild', {
	target: process.versions.node,
	runtime: 'node',

Like so:

var rc = require('rc')('prebuild', { 
  clean: true,
  ...
}

Which isn't strictly required, but keeps us aware of supported options. No additional code is needed for argument parsing, because our parser (minimist) will recognize --no-clean as a boolean out of the box. Then to use the new option, add opts.clean === false ? 'build' : 'rebuild' to 2 places:

prebuild/cmakebuild.js

Line 8 in 8dd24c3

var args = ['build']

prebuild/gypbuild.js

Line 11 in 7c08103

args.push('rebuild')

We could also do opts.clean ? 'rebuild' : 'build' but that would require updating unit tests & the programmatic API (which don't use rc.js).

Lastly, a new unit test would be good to have. For gyp you can copy this test to a new test in the same file.