Avoid user / system files in generated zip

[aduth]

Notably Mac writes .DS_Store files to opened folders. With our current plugin build script, these would be included in archived build folders:

https://github.com/WordPress/gutenberg/blob/master/bin/build-plugin-zip.sh

May be simple enough to add an -x "*.DS_Store argument to the zip command:

https://superuser.com/a/198593

Or we could try to be fancier in accounting for more ignored files / extensions.

[nylen]

I wonder if we could use .gitignore for this.

[aduth]

I thought about that too. Couple problems:

• .DS_Store is part of the global gitignore, not our project's
• Some gitignore we want in zip, like build

[nylen]

Ok then, probably we should just list out the included files more specifically, whether explicitly (one file per line) or using glob patterns like blocks/build/*.{js,css,map} (note, this requires switching the script from #!/bin/sh to #!/bin/bash).

Also I just noticed that this script uses spaces instead of tabs for indentation, we might as well fix that at the same time.

[jasmussen]

See also #952.