use `gcc-ar` from installed tools path

[umbynos]

The tool should already be available, since we use GCC during the compile phase. It should be possible to parse the output from the cli's first compile and grab the path to gcc-ar rcs tool. This way we could avoid the install of another tool. We could use the already implemented approach as a failsafe

[per1234]

I think this would make the tool more friendly to Windows users, though I don't know whether that is really a consideration for the target user.

I actually did a quick attempt to make it to use avr-gcc-ar.exe from the Arduino AVR Boards installation while I was trying the tool out, before deciding to stop messing around and just follow the exact instructions from the readme on my Linux machine.

It should be possible to parse the output from the cli's first compile and grab the path

#8 should make it even easier and more reliable to get the path, since this is already defined in the platform properties.

[umbynos]

For sure, it would be much easier and less hacky, but using the arduino-cli as a library is not that easy since we need the compile command, which should be one of the more complex one.