Bump toolchains/riscv-tools/riscv-isa-sim from 7812eab to 643e6c6#32

dependabot[bot] wants to merge 1 commit intomainucb-eecs151tapeout/ofot-chipyard:mainfrom

dependabot/submodules/toolchains/riscv-tools/riscv-isa-sim-643e6c6ucb-eecs151tapeout/ofot-chipyard:dependabot/submodules/toolchains/riscv-tools/riscv-isa-sim-643e6c6Copy head branch name to clipboard