abuild: fix dep-scanning when sub and main pkg's arch differs

Force dependency scanning when main pkg has noarch but subpackage
overrides it. We need to save the arch setting set in split func for
later if it differs from main pkg's arch in a temp file because the
splitfunc runs in a subprocess.

fixes #4491

abuild.in

@@ -690,6 +690,7 @@ pre_split() {
 	# the subpackages should not inherit those form main package
 	provides=""
 	install_if=""
+	apkbuild_arch="$arch"
 }
 
 prepare_subpackages() {
@@ -796,6 +797,11 @@ prepare_metafiles() {
 #		parch="noarch"
 #	fi
 
+	# save arch incase subpackages set it different than main pkg
+	if [ "${apkbuild_arch:-$arch}" != "$arch" ]; then
+		echo "$arch" > "$controldir"/.arch
+	fi
+
 	echo "# Generated by $(basename $0) $program_version" >"$pkginfo"
 	if [ -n "$FAKEROOTKEY" ]; then
 		echo "# using $($FAKEROOT -v)" >> "$pkginfo"
@@ -1115,7 +1121,7 @@ scan_shared_objects() {
 	local name="$1" controldir="$2" datadir="$3"
 	local opt= i=
 
-	if [ "$arch" = "noarch" ]; then
+	if [ "$arch" = "noarch" ] && ! [ -e "$controldir"/.arch ]; then
 		return 0
 	fi