Update for prebuildify@3

[vweevers]

• [ ] Tag images with version number
• [ ] Use new environment variables
  • [ ] Rename TARGET_PLATFORM to PREBUILD_PLATFORM
  • [ ] Rename ARM_VERSION to PREBUILD_ARMV
  • [ ] Rename ARCH to PREBUILD_ARCH
  • [ ] Rename STRIP to PREBUILD_STRIP_BIN
• [x] Add prebuild tags Not here

Alternatively, we can keep the old env vars for compat, until we figure out autobuilds/versioning/tagging later.