make the makefile dep more robust

Change-Id: Iabf62eb089530dff97c0a920b2be9c239b02d5b8

solenv/gbuild/UnpackedTarball.mk

@@ -167,6 +167,11 @@ $(call gb_UnpackedTarball_get_clean_target,%) :
 			$(call gb_UnpackedTarball_get_dir,$*) \
 	)
 
+define gb_UnpackedTarball__get_makefile
+$(lastword $(foreach makefile,$(MAKEFILE_LIST),$(if $(filter UnpackedTarball_%,$(notdir $(makefile))),$(makefile))))
+
+endef
+
 # Initialize unpacked tarball
 define gb_UnpackedTarball_UnpackedTarball_internal
 $(call gb_UnpackedTarball_get_target,$(1)) : UNPACKED_CXX_SUFFIX :=
@@ -177,7 +182,7 @@ $(call gb_UnpackedTarball_get_target,$(1)) : UNPACKED_PATCHES :=
 $(call gb_UnpackedTarball_get_target,$(1)) : UNPACKED_PATCHLEVEL := $(gb_UnpackedTarball_PATCHLEVEL_DEFAULT)
 $(call gb_UnpackedTarball_get_target,$(1)) : UNPACKED_POST_ACTION :=
 
-$(call gb_UnpackedTarball_get_preparation_target,$(1)) : $(lastword $(MAKEFILE_LIST))
+$(call gb_UnpackedTarball_get_preparation_target,$(1)) : $(call gb_UnpackedTarball__get_makefile)
 $(call gb_UnpackedTarball_get_preparation_target,$(1)) :| $(dir $(call gb_UnpackedTarball_get_target,$(1))).dir
 $(call gb_UnpackedTarball_get_target,$(1)) : $(call gb_UnpackedTarball_get_preparation_target,$(1))
 $(call gb_UnpackedTarball_get_target,$(1)) :| $(dir $(call gb_UnpackedTarball_get_target,$(1))).dir