Prevent ameba from being installed during postinstall

[jwoertink]

Purpose

Fixes #1524

Description

When Lucky is included as a dependency of an app, and you run shards install, it will call Lucky's postinstall script. That will then run shards build from within the lucky directory causing it to install all shards including development dependencies.

This PR tells it to only build the targets, but don't build development dependencies.

Checklist

• - An issue already exists detailing the issue/or feature request that this PR fixes
• - All specs are formatted with crystal tool format spec src
• - Inline documentation has been added and/or updated
• - Lucky builds on docker with ./script/setup
• - All builds and specs pass on docker with ./script/test

[robacarp]

Since the typical use case here would be to build without development, should this if be reversed so that the flag doesn't need to be passed in unless you actually want the ancillary binaries?

Do we even need the flag here? Assuming that I actually want the ameba binary I can add that to my own shards.build stanza for the project.

[jwoertink]

My bash skills suck 😅 it should probably be flipped

@edwardloveall and I were talking about this, and we figured if you're working on Lucky directly, maybe there's a time you want to run that script with any dev deps included? I think the 99% case though would be without.