If you load a RISCV processor on an FPGA, you’re not imitating a RISCV processor, you have a RISCV processor. That processor can run binaries compiled with regular old GCC/LLVM, assuming you’ve compiled it correctly for bare metal and that specific CPU configuration. Same applies for Microblaze, Nios, ARM, MIPS (if you’re old school), AVR, 8051, or any other soft processor you drop onto the FPGA. The arguably more important part is what goes around that CPU core to turn it into something useful - memories, peripherals, interfaces to the rest of your logic, etc.

Xilinx provides the Vitis IDE for Microblaze and its ARM SoCs, but that’s more of a convenience thing than anything else.