makepkg: write makedepends into .PKGINFO

Currently there is no way to access the makedepends for a package
apart from parsing its PKGBUILD. Put these into the .PKGINFO file
with the idea of making them available in the repo dbs so that
automated build tools can readily determine build order.

Signed-off-by: Allan McRae <allan@archlinux.org>
Signed-off-by: Dan McGee <dan@archlinux.org>

scripts/makepkg.sh.in

@@ -1276,6 +1276,8 @@ write_pkginfo() {
 		fi
 	done
 
+	[[ $makedepends ]]  && printf "makedepend = %s\n"  "${makedepends[@]}"
+
 	for it in "${packaging_options[@]}"; do
 		check_option "$it" "y"
 		case $? in