Option to print out which styles are being built

[almccon]

Pulling out this comment from discussion in https://github.com/stamen/aws-map-styles/pull/1060.

Basically, in our workflows we almost always run build-styles followed by clean-styles, and while the clean script outputs a list of filenames that it's cleaning, the earlier and much longer-running build script does not.

Timing it for one example: I get 45 seconds of no output while it's building the styles, and then when it starts cleaning them, I get 7 seconds of filenames outputted so I can see progress. Then it's finished. Since the build process is so much longer than the clean process, I'd also like to see the filenames printed when the build is happening, and then see them printed again when they're getting cleaned.

[aparlato]

@almccon we do currently have a --v (verbose) option for a verbose output which will:

• print the style name
• print every layer getting added to that style

Admittedly, this might be more information than is really helpful, but it would solve the problem of visibility into what the script is doing during that waiting period.

So the 2 options here are:

• Leave as is and use the verbose option already in place
• Add an argument for the verbose option to only print style names and not layers

What do you think?