Similar to the Arty S7, the Arty A7 comes in two variants: one with the Xilinx Artix A7 XC7A35TI SKU and the other with the Xilinx Artix A7 XC7A100TI SKU. I have a board with the latter, and ran the Blinky test to be sure that the following commit does not contain any regressions.

Basically the commit follows the same structure as the arty_s7 board by changing ArtyA7Platform to _ArtyA7Platform and not setting the device constant. Then it introduces ArtyA7_35Platform and ArtyA7_100Platform for the two different variants, inheriting _ArtyA7Platform and setting the device constant to the appropriate SKU for that platform. Finally, the test has been changed to default to running Blinky on the ArtyA7_35Platform.