Ariel

Support for referencing other variants in boards.txt

12

The **boards.txt** file allows the following syntax `pinoccio.build.core=arduino:arduino` to reference a core e.g. from the main Arduino SDK (see [this](https://github.com/arduino/Arduino/wiki/Arduino-IDE-1.5-3rd-party-Hardware-specification#referencing-another-core-variant-or-tool) for the detailed description). Currently arduino-cmake chokes on that syntax,...