ISTR that the avionics code is written in Ada, and runs on top of Intel i960 processors, and that the Ada compiler for that target only runs on VAX/VMS (not even OpenVMS, but specifically VMS on the VAX).
Anyway, the processors in the F-22A are a mix of different cores. The power supply in the Gen 3 radar used a MIL-STD-1750A processor. The PICC[1] processor modules also used the MIL-STD-1750A originally, but moved to a newer processor in a refresh (if I remember correctly). I don't know what the non-Raytheon components of the plane were using.
As for the compiler, you are spot-on. We had a MicroVAX in a vault (it was a cleared computing system) just in case we needed to recompile the embedded software for the power supply controller.
[1] Unfortunately, I don't remember what this acronym expands to.
(Or does "MISRA" stand for something else?)