community/neovim: build with lua on riscv64

Inspired by Arch Linux (and s390x):

• https://github.com/felixonmars/archriscv-packages/commit/25a5df43375d7014ad4a23845817815dd18129e4
• https://github.com/felixonmars/archriscv-packages/commit/3215407ea4fd1db166af9ce95eb23c9e68edbb35