Support reproducible builds

Recent development versions of makepkg support reproducible builds
through the environment variable SOURCE_DATE_EPOCH. Pass this variable
through makechrootpkg to makepkg when available.

Also initialize SOURCE_DATE_EPOCH whenever running archbuild to enforce
reproducible builds for repository packages.

Signed-off-by: Eli Schwartz <eschwartz@archlinux.org>
Signed-off-by: Levente Polyak <anthraxx@archlinux.org>

archbuild.in

@@ -39,7 +39,7 @@ while getopts 'hcr:' arg; do
 	esac
 done
 
-check_root
+check_root SOURCE_DATE_EPOCH
 
 # Pass all arguments after -- right to makepkg
 makechrootpkg_args+=("${@:$OPTIND}")
@@ -74,5 +74,10 @@ else
                 pacman -Syu --noconfirm || abort
 fi
 
+# Always build official packages reproducibly
+if [[ ! -v SOURCE_DATE_EPOCH ]]; then
+	export SOURCE_DATE_EPOCH=$(date +%s)
+fi
+
 msg "Building in chroot for [%s] (%s)..." "${repo}" "${arch}"
 exec makechrootpkg -r "${chroots}/${repo}-${arch}" "${makechrootpkg_args[@]}"

lib/archroot.sh

@@ -6,13 +6,15 @@
 CHROOT_VERSION='v4'
 
 ##
-#  usage : check_root
+#  usage : check_root $keepenv
 ##
 orig_argv=("$0" "$@")
 check_root() {
+	local keepenv=$1
+
 	(( EUID == 0 )) && return
 	if type -P sudo >/dev/null; then
-		exec sudo -- "${orig_argv[@]}"
+		exec sudo --preserve-env=$keepenv -- "${orig_argv[@]}"
 	else
 		exec su root -c "$(printf ' %q' "${orig_argv[@]}")"
 	fi

makechrootpkg.in

@@ -205,6 +205,7 @@ EOF
 	{
 		printf '#!/bin/bash\n'
 		declare -f _chrootbuild
+		declare -p SOURCE_DATE_EPOCH 2>/dev/null
 		printf '_chrootbuild "$@" || exit\n'
 
 		if $run_namcap; then
@@ -231,7 +232,7 @@ _chrootbuild() {
 	# use "$" in arguments to commands with "sudo -i".  ${foo} or
 	# ${1} is OK, but $foo or $1 isn't.
 	# https://bugzilla.sudo.ws/show_bug.cgi?id=765
-	sudo -iu builduser bash -c 'cd /startdir; makepkg "$@"' -bash "$@"
+	sudo --preserve-env=SOURCE_DATE_EPOCH -iu builduser bash -c 'cd /startdir; makepkg "$@"' -bash "$@"
 }
 
 _chrootnamcap() {
@@ -343,7 +344,7 @@ main() {
 	[[ -n $makepkg_user && -z $(id -u "$makepkg_user") ]] && die 'Invalid makepkg user.'
 	makepkg_user=${makepkg_user:-${SUDO_USER:-$USER}}
 
-	check_root
+	check_root SOURCE_DATE_EPOCH
 
 	# Canonicalize chrootdir, getting rid of trailing /
 	chrootdir=$(readlink -e "$passeddir")