If by configure, on the other hand, you mean to actually use the Arduino IDE as a development environment for 8051s, you can forget it. 8051 is a different architecture than AVR and Arduino only supports AVR.
I can tell you from experience, you can use this compiler:http://en.wikipedia.org/wiki/MCU_8051_IDE
You will need a ROM programmer to upload the result binary to it. It doesn't use an a debugger/emulator like AVRISP or AVR JTAGICE.
Have fun being an 8051 hobbyist.
A board I made out of a similar Atmel 8051 chip using the compiler above, programmed using a ChipMax programmer: