https://digilent.com/reference/programmable-logic/arty-a7/reference-manual
.bit, .bin, and .mcs are supported for FLASH.
By default the data is written to a volatile flash. This is erased on power cycle.
Adding the -f flag to open FPGA loader, wries it to the external onboard SPIFlash.
this allowes it to retai the code even aafter a power cycle.
F4PGA loader installs a deprecated version of openFPGAloder...using sudo uses the new version.