avrdude: add libserialport dep

[MCUdude]

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Avrdure needs to be built with libserialport to provide a richer serial port experience

[MCUdude]

BTW, the libserialport version that brew builds is 0.1.1, and is old. On top of that, I recently discovered a libserialport bug (with every simple fix) that makes it useless for many USB-to-serial adapters on macOS.

Ideally, that PR should be merged immediately as the solution is obvious. However, I'm not able to get in touch with any of the developers. I've tried to tag them on Github, and reach out by sending an email, but without luck.

Would it be possible to provide a fork of libserialport that Avrdude could rely on, instead of the broken 0.1.1 version? The Avrdude project could absolutely host their own, known good version of libserialport.

I'm new to the whole contributing side of things here, so I don't know what your policy is on forks.

[chenrui333]

@MCUdude 👋 thanks for your first PR to homebrew-core! Can you squash your commits into one and use "avrdude: add libserialport dep" as commit msg? Thanks!

[MCUdude]

@chenrui333 The more I try to fix the commit history, the more comments from others are added to this PR!
Do you know how to fix this, or do I have to create a new PR?