https://github.com/stern/stern/releases/tag/v1.32.0

https://github.com/stern/stern/releases/tag/v1.31.0

https://github.com/stern/stern/releases/tag/v1.30.0

Changes to PKGBUILD:

- Use SPDX license identifier.
- Move options array to correct place.
  See: https://gitlab.archlinux.org/pacman/pacman/raw/master/proto/PKGBUILD.proto
- Use GitHub's tarball instead of upstream's.
- Vendor dependencies in prepare() to avoid downloads in build() and check().
- Improve debup package support by declaring GOPATH, -compressdwarf=false and
  removing -trimpath.
- Break some long lines.