xbps-src: make -D install work with bootstrap subpkgs.

xbps-src/libexec/xbps-src-doinst-helper.sh.in

@@ -129,8 +129,9 @@ install_src_phase()
 			spkgrev="${subpkg}-${version}"
 		fi
 		check_installed_pkg ${spkgrev}
-		[ $? -eq 0 ] && continue
-
+		if [ $? -eq 0 -a -z "$BOOTSTRAP_PKG_REBUILD" ]; then
+			continue
+		fi
 		msg_normal "'${sourcepkg}-$lver': preparing subpackage '${subpkg}'...\n"
 		if [ ! -f $XBPS_SRCPKGDIR/${sourcepkg}/${subpkg}.template ]; then
 			msg_error "Cannot find '${subpkg}' subpkg build template!\n"