common.mk: ignore capi failure

* common.mk (capi): ignore doxygen failure (temporarily).

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@44624 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

common.mk

@@ -198,6 +198,7 @@ capi: $(CAPIOUT)/.timestamp PHONY
 $(CAPIOUT)/.timestamp: Doxyfile $(PREP)
 	$(Q) $(MAKEDIRS) "$(@D)"
 	$(ECHO) generating capi
+	- \
 	$(Q) $(DOXYGEN) -b
 	$(Q) $(MINIRUBY) -e 'File.open(ARGV[0], "w"){|f| f.puts(Time.now)}' "$@"