add missing $(if) check for build logging

SVN-Revision: 15366

include/subdir.mk

@@ -35,7 +35,7 @@ define subdir
       )
       $(call warn_eval,$(1)/$(bd),t,T,$(1)/$(bd)/$(target): $(if $(QUILT),,$($(1)/$(bd)/$(target)) $(call $(1)//$(target),$(1)/$(bd))))
 	  	$(if $(BUILD_LOG),@mkdir -p $(TOPDIR)/logs/$(1)/$(bd))
-		+$$(SUBMAKE) -C $(1)/$(bd) $(target) SILENT= 2>&1 | tee $(TOPDIR)/logs/$(1)/$(bd)/$(target).txt $(if $(findstring $(bd),$($(1)/builddirs-ignore-$(target))), || $(call MESSAGE,   ERROR: $(1)/$(bd) failed to build.))
+		+$$(SUBMAKE) -C $(1)/$(bd) $(target) $(if $(BUILD_LOG),SILENT= 2>&1 | tee $(TOPDIR)/logs/$(1)/$(bd)/$(target).txt) $(if $(findstring $(bd),$($(1)/builddirs-ignore-$(target))), || $(call MESSAGE,   ERROR: $(1)/$(bd) failed to build.))
         $$(if $(call debug,$(1)/$(bd),v),,.SILENT: $(1)/$(bd)/$(target))
 
       # legacy targets