Add support for passing arguments to waf in Makefile
https://bugzilla.samba.org/show_bug.cgi?id=9886

Index: Makefile
--- Makefile.orig
+++ Makefile
@@ -1,7 +1,8 @@
 # simple makefile wrapper to run waf
 
 WAF_BINARY=$(PYTHON) ./buildtools/bin/waf
-WAF=PYTHONHASHSEED=1 WAF_MAKE=1 $(WAF_BINARY)
+WAF_ARGS?=
+WAF=PYTHONHASHSEED=1 WAF_MAKE=1 $(WAF_BINARY) $(WAF_ARGS)
 
 all:
 	$(WAF) build