Allow parallel make all to build each subdir simultaneously
diff --git a/Makefile b/Makefile
index 518e08c..5a95087 100644
--- a/Makefile
+++ b/Makefile
@@ -2,7 +2,11 @@
 
 include config.mk
 
-all clean install uninstall:
+all: $(addsuffix .all,$(SUBDIRS))
+$(addsuffix .all,$(SUBDIRS)):
+	$(MAKE) -C $(basename $@) all
+
+clean install uninstall:
 	for dir in $(SUBDIRS); do \
 		$(MAKE) -C $$dir $@ || exit; \
 	done