nmake doesn't understand $<

Fix MSVC build error.

common.mk

@@ -1087,7 +1087,7 @@ known_errors.inc: $(srcdir)/template/known_errors.inc.tmpl $(srcdir)/defs/known_
 
 vm_call_iseq_optimized.inc: $(srcdir)/template/call_iseq_optimized.inc.tmpl
 	$(ECHO) generating $@
-	$(Q) $(BASERUBY) $(tooldir)/generic_erb.rb -c -o $@ $<
+	$(Q) $(BASERUBY) $(tooldir)/generic_erb.rb -c -o $@ $(srcdir)/template/call_iseq_optimized.inc.tmpl
 
 $(MINIPRELUDE_C): $(COMPILE_PRELUDE) $(BUILTIN_RB_SRCS)
 	$(ECHO) generating $@