rvvm: Add RVVM recipe

This MR adds a recipe to build RVVM (RISC-V Virtual Machine).

Tested features:

• GUI (Via SDL1, other backends are not working well due to lack of dynamic linking)
• JIT (Full guest acceleration)

Disabled features:

• Building librvvm (Due to lack of dynamic linking)
• Userland networking (Something in Redox causes RVVM networking stack to hang)

mentioned in commit 2b5d5691

merged