Update GHA scripts to use `bashbrew-buildkit-env-setup.sh`

If our DOI checkout includes the new `bashbrew-buildkit-env-setup.sh` script, we should use it to set up our buildkit-related environment variables.

scripts/github-actions/generate.sh

@@ -148,6 +148,19 @@ done
 
 strategy="$(
 	for tag in "${order[@]}"; do
+		# envObjectToGitHubEnvFileJQ converts from the output of ~/oi/.bin/bashbrew-buildkit-env-setup.sh into what GHA expects in $GITHUB_ENV
+		# (in a separate env to make embedding/quoting easier inside this sub-jq that generates JSON that embeds shell scripts)
+		envObjectToGitHubEnvFileJQ='
+			to_entries | map(
+				(.key | if test("[^a-zA-Z0-9_]+") then
+					error("invalid env key: \(.)")
+				else . end)
+				+ "="
+				+ (.value | if test("[\r\n]+") then
+					error("invalid env value: \(.)")
+				else . end)
+			) | join("\n")
+		' \
 		jq -c '
 			.meta += {
 				froms: (
@@ -176,8 +189,23 @@ strategy="$(
 					),
 					"git clone --depth 1 https://github.com/docker-library/official-images.git -b master ~/oi",
 
-					# https://github.com/docker-library/bashbrew/pull/43
-					"echo BASHBREW_BUILDKIT_SYNTAX=\"$(< ~/oi/.bashbrew-buildkit-syntax)\" >> \"$GITHUB_ENV\"",
+					(
+						"# https://github.com/docker-library/bashbrew/pull/43",
+						if ([ .meta.entries[].builder ] | index("buildkit")) then
+							# https://github.com/docker-library/bashbrew/pull/70#issuecomment-1461033890 (we need to _not_ set BASHBREW_ARCH here)
+							"if [ -x ~/oi/.bin/bashbrew-buildkit-env-setup.sh ]; then",
+							"\t# https://github.com/docker-library/official-images/pull/14212",
+							"\tbuildkitEnvs=\"$(~/oi/.bin/bashbrew-buildkit-env-setup.sh)\"",
+							"\tjq <<<\"$buildkitEnvs\" -r \(env.envObjectToGitHubEnvFileJQ | @sh) | tee -a \"$GITHUB_ENV\"",
+							"else",
+							"\tBASHBREW_BUILDKIT_SYNTAX=\"$(< ~/oi/.bashbrew-buildkit-syntax)\"; export BASHBREW_BUILDKIT_SYNTAX",
+							"\tprintf \"BASHBREW_BUILDKIT_SYNTAX=%q\\n\" \"$BASHBREW_BUILDKIT_SYNTAX\" >> \"$GITHUB_ENV\"",
+							"fi",
+							empty
+						else
+							empty
+						end
+					),
 
 					"# create a dummy empty image/layer so we can --filter since= later to get a meaningful image list",
 					"{ echo FROM " + (