Check if AVR Toolchain exists in macOS

[enekochan]

AVR Toolchain for macOS can also be installed from Microchip binaries in https://www.microchip.com/mplab/avr-support/avr-and-arm-toolchains-c-compilers

[edgar-bonet]

If avr-gcc is in the $PATH (it can be found by which), shouldn't AVR be just “avr-”, like in the non-MacOS case?

[enekochan]

If avr-gcc is in the $PATH (it can be found by which), shouldn't AVR be just “avr-”, like in the non-MacOS case?

Yes, that works too and is even simpler :) Just followed the same way as done for Macports and Homebrew.

[enekochan]

@buserror Should I change this PR to what @edgar-bonet proposed?

[buserror]

@enekochan yes please. Wonder how long that bug has been in ;-)

[enekochan]

@buserror Done :)

[enekochan]

@buserror Is there a problem to merge this?