Hi Marcus,
Arduino 101 toolchains and upload tools are not yet compiled for ARM architectures (which is still in beta)
At the moment you'll need to compile the toolchain on RPi (sources here) and the golang based upload tool (here ) , place them in the correct folder structure and launch the IDE.
Otherwise, if you don't need to get things working tomorrow, open an issue on GitHub - arduino/ArduinoCore-arc32 and if it gets enough traction the next version could be ARM-compatible.