makerepropkg: use correct devtools makepkg.conf files from dist

Use the recorded buildtool in order to download the matching dist
package and use the appropriate makepkg.conf for reproducing the
package. This is required as the flags are not recorded in the BUILDINFO
hence we need to provide the matching config that declared those flags.

Makefile

@@ -1,4 +1,5 @@
 V=20210202
+BUILDTOOLVER ?= $(V)-git
 
 PREFIX = /usr/local
 MANDIR = $(PREFIX)/share/man
@@ -92,7 +93,7 @@ edit = sed -e "s|@pkgdatadir[@]|$(PREFIX)/share/devtools|g"
 %: %.in Makefile lib/common.sh
 	@echo "GEN $@"
 	@$(RM) "$@"
-	@{ echo -n 'm4_changequote([[[,]]])'; cat $@.in; } | m4 -P --define=m4_devtools_version=$V | $(edit) >$@
+	@{ echo -n 'm4_changequote([[[,]]])'; cat $@.in; } | m4 -P --define=m4_devtools_version=$(BUILDTOOLVER) | $(edit) >$@
 	@chmod a-w "$@"
 	@chmod +x "$@"
 	@bash -O extglob -n "$@"

makerepropkg.in

@@ -185,7 +185,22 @@ for fname in "${installed[@]}"; do
         exit 1
     fi
 done
-printf '%s\n' "${allpkgfiles[@]}" | mkarchroot -M @pkgdatadir@/makepkg-x86_64.conf -U "${archroot_args[@]}" "${buildroot}"/root - || exit 1
+
+trap 'rm -rf $TEMPDIR' EXIT INT TERM QUIT
+TEMPDIR=$(mktemp -d --tmpdir makerepropkg.XXXXXXXXXX)
+
+makepkg_conf=@pkgdatadir@/makepkg-x86_64.conf
+if [[ "${BUILDTOOL}" = devtools ]]; then
+    fname=${BUILDTOOL}-${BUILDTOOLVER}
+    if ! buildtool_file=$(get_pkgfile "${fname}"); then
+        error "failed to retrieve ${fname}"
+        exit 1
+    fi
+    msg2 "using makepkg.conf from ${fname}"
+    makepkg_conf="${TEMPDIR}/makepkg.conf"
+    bsdtar xOqf "${buildtool_file/file:\/\//}" usr/share/devtools/makepkg-x86_64.conf > "${makepkg_conf}"
+fi
+printf '%s\n' "${allpkgfiles[@]}" | mkarchroot -M "${makepkg_conf}" -U "${archroot_args[@]}" "${buildroot}"/root - || exit 1
 
 # use makechrootpkg to prep the build directory
 makechrootpkg -r "${buildroot}" -l "${chroot}" -- --packagelist || exit 1