[Feature] Support Platform.local.txt

[cuttingedge1109]

Hi there.
By using platform.local.txt file, we can override properties defined in platform.txt or define new properties without modifying platform.txt, as you know.
If the action supports platform-file section to import custom platform.local.txt file, it would be more flexible and powerful.
Regards.

[per1234]

Hi @cuttingedge1109. I have seen multiple requests for this sort of control over the build properties, including most recently #16

In order to accommodate these use cases, I added the cli-compile-flags input: #18
This input allows you to define or override any build property via the --build-property flag of the arduino-cli compile command used by the action to compile the sketches:
https://arduino.github.io/arduino-cli/latest/commands/arduino-cli_compile/#options

So, from what I can see, the action already provides the capability you request, without the inconvenience of having to store platform.local.txt files in the repository or generate them on the fly.

If you find a real life use case that the current capabilities don't support, but the platform.local.txt approach would, please share it here and I'll investigate and give the request further consideration.