archbuild: prefer repo/arch-specific configs if they exist

When mixing and matching different repos and architectures not present
in mainline archlinux, it is sometimes desirable to set up differing
presets with more granularity than devtools currently allows.

One example of this is when building for architectures that are only
supported by another project -- in order to coexist on a mainline
archlinux host, a different mirrorlist needs to be used.

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

archbuild.in

@@ -20,6 +20,15 @@ fi
 chroots='/var/lib/archbuild'
 clean_first=false
 
+pacman_config="@pkgdatadir@/pacman-${repo}.conf"
+if [[ -f @pkgdatadir@/pacman-${repo}-${arch}.conf ]]; then
+    pacman_config="@pkgdatadir@/pacman-${repo}-${arch}.conf"
+fi
+makepkg_config="@pkgdatadir@/makepkg-${arch}.conf"
+if [[ -f @pkgdatadir@/makepkg-${repo}-${arch}.conf ]]; then
+    makepkg_config="@pkgdatadir@/makepkg-${repo}-${arch}.conf"
+fi
+
 usage() {
 	echo "Usage: $cmd [options] -- [makechrootpkg args]"
 	echo '    -h         This help'
@@ -61,15 +70,15 @@ if ${clean_first} || [[ ! -d "${chroots}/${repo}-${arch}" ]]; then
 	rm -rf --one-file-system "${chroots}/${repo}-${arch}"
 	mkdir -m755 -p "${chroots}/${repo}-${arch}"
 	setarch "${arch}" mkarchroot \
-		-C "@pkgdatadir@/pacman-${repo}.conf" \
-		-M "@pkgdatadir@/makepkg-${arch}.conf" \
+		-C "${pacman_config}" \
+		-M "${makepkg_config}" \
 		"${chroots}/${repo}-${arch}/root" \
 		"${base_packages[@]}" || abort
 else
 	lock 9 "${chroots}/${repo}-${arch}/root.lock" "Locking clean chroot"
 	arch-nspawn \
-		-C "@pkgdatadir@/pacman-${repo}.conf" \
-		-M "@pkgdatadir@/makepkg-${arch}.conf" \
+		-C "${pacman_config}" \
+		-M "${makepkg_config}" \
 		"${chroots}/${repo}-${arch}/root" \
 		pacman -Syuu --noconfirm || abort
 fi