Update for SDK 2.3.1

Switch RISC-V toolchain triple to riscv32-pico-elf, and fix newlib misalignment issues - see #28

Update for SDK 2.3.0

Build OpenOCD so it can auto-detect it's script directory, and update riscv-gnu-toolchain version

Fix jimtcl library issues, and create universal MacOS builds of everything

Add --enable-strip to Risc-V toolchain build, and improve shared library handling on MacOS and Linux

Switch Windows build to UCRT64, and update picotool with A4 support

Use SDK and picotool 2.2.0

Add x64 MacOS builds of OpenOCD and Risc-V toolchain

Update Risc-V toolchain and OpenOCD builds