Make makepkg compute sizes properly

Makepkg used to use du --apparent-size to compute the size of the
package. Unfortunately, this would result in different sizes depending
on the filesystem used (e.g., btrfs vs ext4), which would affect
reproducible builds. Use a wc-based approach to compute sizes

Signed-off-by: Santiago Torres <santiago@archlinux.org>
Signed-off-by: Allan McRae <allan@archlinux.org>

scripts/makepkg.sh.in

@@ -588,8 +588,7 @@ write_kv_pair() {
 }
 
 write_pkginfo() {
-	local size="$(@DUPATH@ @DUFLAGS@)"
+	local size="$(find . -type f -exec cat {} + 2>/dev/null | wc -c)"
-	size="$(( ${size%%[^0-9]*} * 1024 ))"
 
 	merge_arch_attrs