Fix an issue in setting up PATH.

`PATH=$(foreach p,$(INTERNAL_USERIMAGES_BINARY_PATHS),$(p):)$$PATH` will
produce a space separated string due to `foreach`, if
$(INTERNAL_USERIMAGES_BINARY_PATHS) has more than one string. We didn't
hit the issue in the past because $(INTERNAL_USERIMAGES_BINARY_PATHS)
had contained only one path in practice.

Test: TreeHugger
Change-Id: I74ef4356668af63d871a81f6bfd4c9324aa1d956
diff --git a/core/tasks/oem_image.mk b/core/tasks/oem_image.mk
index e9c506a..489feeb 100644
--- a/core/tasks/oem_image.mk
+++ b/core/tasks/oem_image.mk
@@ -34,7 +34,7 @@
 	@mkdir -p $(TARGET_OUT_OEM)
 	@mkdir -p $(oemimage_intermediates) && rm -rf $(oemimage_intermediates)/oem_image_info.txt
 	$(call generate-image-prop-dictionary, $(oemimage_intermediates)/oem_image_info.txt,oem,skip_fsck=true)
-	$(hide) PATH=$(foreach p,$(INTERNAL_USERIMAGES_BINARY_PATHS),$(p):)$$PATH \
+	$(hide) PATH=$(INTERNAL_USERIMAGES_BINARY_PATHS):$$PATH \
 	  build/make/tools/releasetools/build_image.py \
 	  $(TARGET_OUT_OEM) $(oemimage_intermediates)/oem_image_info.txt $@ $(TARGET_OUT)
 	$(hide) $(call assert-max-image-size,$@,$(BOARD_OEMIMAGE_PARTITION_SIZE))