If an ABI isn't specified in the target then the program fails to start with "Error relocating"

  - relro is now supported upstream, so we can use `zig build`
  - need to introduce pie patch

archlinux/devtools!109 (comment 74475)

  - The hardening patch was unused with the moved to invoking `zig build-exe`
  - Need to specify kernel version or it defaults to 3.16.
    I selected 5.10 as it is one linux-lts release behind
  - Should specify gnu ABI to prevent incorrect auto-detection in some environments
  - Need to specify glibc version or it defaults to 2.19
  - When using non-native target and skipping build.zig, need to specify lib/include search dirs

mark as adopted from vesath
add additional b2 checksum to verify multiple checksums worth of TOFU
cosmetic fixes, e.g. MIT isn't a custom label, add PGP key intended uid...

FTR, commands used to change arch=() and then verify the changes:

$ sed -Ei "/^arch=/{s/ *?['\"]?i686['\"]? *?//;s/ *$//}" */*/PKGBUILD*

$ grep -r i686 * | grep arch= | grep -v repos

$ svn diff | grep -A 1 ^-[^-] | grep -v -- -- | cut -c2- |
  while IFS=$'\n' read -r l1; IFS=$'\n' read -r l2; do
    echo "$l1 -> $l2"
  done | sort -u