Ensure source tree is built before running make dist

Makefile.am

@@ -36,6 +36,11 @@ distcleancheck_listfiles = \
 	find . -type f -exec sh -c 'test -f $(srcdir)/$$1 || echo $$1' \
 		sh '{}' ';'
 
+# XXX: This is a hack to ensure we have a built source tree when
+# running make dist If we had used non-recursive make we could have
+# solved it better, but we don't, so use this at least for now.
+LICENSE: all
+
 cscope:
 	-rm -f cscope*
 	find . -name '*.[hcS]' > cscope.files