fixing error handling for generated files again

solenv/gbuild/CustomTarget.mk

@@ -59,8 +59,8 @@ $(if $(filter $(2),$(gb_CustomTarget_REPOSITORYNAMES)),,\
 gb_CustomTarget_REPO_$(1) := $(2)
 $(call gb_CustomTarget_get_target,$(1)) : \
   $(call gb_CustomTarget__get_makefile,$($(2)),$(1))
-$(call gb_CustomTarget_get_workdir,$(1))/% : \
-  $(call gb_CustomTarget_get_target,$(1))
+$(call gb_CustomTarget_get_workdir,$(1))/% : $(call gb_CustomTarget_get_target,$(1))
+	test -f $@ || (echo "Missing file $@ which should have been generated from CustomTarget $(1), but was not." && false)
 endef
 
 

solenv/gbuild/LinkTarget.mk

@@ -197,7 +197,7 @@ gb_GenCObject_get_source = $(WORKDIR)/$(1).c
 #  gb_CObject__command
 
 $(call gb_GenCObject_get_target,%) : $(call gb_GenCObject_get_source,%)
-	$(if $(wildcard $<),,$(eval $(call gb_Output_error,No such source file $<)))
+	test -f $< || (echo "Missing generated source file $<" && false)
 	$(call gb_CObject__command,$@,$*,$<,$(call gb_GenCObject_get_dep_target,$*))
 
 ifeq ($(gb_FULLDEPS),$(true))
@@ -216,7 +216,7 @@ gb_GenCxxObject_get_source = $(WORKDIR)/$(1).cxx
 #  gb_CxxObject__command
 
 $(call gb_GenCxxObject_get_target,%) : $(call gb_GenCxxObject_get_source,%)
-	$(if $(wildcard $<),,$(eval $(call gb_Output_error,No such source file $<)))
+	test -f $< || (echo "Missing generated source file $<" && false)
 	$(call gb_CxxObject__command,$@,$*,$<,$(call gb_GenCxxObject_get_dep_target,$*))
 
 ifeq ($(gb_FULLDEPS),$(true))