make-archive: Build reproducible tarball

Remove timestamps, user names, etc. from the tarball so that
it can be built reproducibly by multiple people, on different
machines.

The outer bzip2 layer might still be different, no reproducible
bzip2 known.

Signed-off-by: Julian Andres Klode <julian.klode@canonical.com>

make-archive

@@ -86,14 +86,16 @@ main() {
  cd ..
  if [ "x" = "x${SHIM_GIT_TAG}" ] ; then
  git archive --format=tar "$(git log -1 --pretty=format:%h)" | ( cd "${ARCHIVE_DIR}/shim-${VERSION}" ; tar x )
+ TIMESTAMP=0
  else
  # ORIGIN doesn't yet have this tag
  git archive --format=tar "${SHIM_GIT_TAG}" | ( cd "${ARCHIVE_DIR}/shim-${VERSION}" ; tar x )
+ TIMESTAMP=$(git log -1 --pretty=%ct "${SHIM_GIT_TAG}")
  fi
  git log -1 --pretty=format:%H > "${ARCHIVE_DIR}/shim-${VERSION}/commit"
  DIR="$PWD"
  cd "${ARCHIVE_DIR}"
- tar -c --bzip2 -f "${DIR}/shim-${VERSION}.tar.bz2" "shim-${VERSION}"
+ tar -c --sort=name --mtime="@${TIMESTAMP}" --owner=0 --group=0 --numeric-owner --pax-option=exthdr.name=%d/PaxHeaders/%f,delete=atime,delete=ctime --bzip2 -f "${DIR}/shim-${VERSION}.tar.bz2" "shim-${VERSION}"
  rm -rf "${ARCHIVE_DIR}"
  echo "The archive is in shim-${VERSION}.tar.bz2"
  exit 0