pmb: enable riscv64 architecture
Enable pmbootstrap to work on riscv64 packages, and at the same time also expand the alpine_to_hostspec list to match upstream (adding riscv32 and loongarch*).
Enable pmbootstrap to work on riscv64 packages, and at the same time also expand the alpine_to_hostspec list to match upstream (adding riscv32 and loongarch*).