scripts: Makefile.lib: Add dependency for DTS overlay

This patch adds a dependency for the DTS overlay so that the DTS is
compiled when the state of the overlay file changes.

Change-Id: I2affe67f90f56b1d97384d5cd4e3026abed24253
Signed-off-by: Andy Gross <[email protected]>

Author: Andy Gross

scripts/Makefile.lib

@@ -282,9 +282,11 @@ cmd_dt_S_dtb=						\
 $(obj)/%.dtb.S: $(obj)/%.dtb
 	$(call cmd,dt_S_dtb)
 
+DTS_OVERLAY ?= $(PROJECT_BASE)/$(BOARD_NAME).overlay
+
 quiet_cmd_dtc = DTC     $@
 cmd_dtc = echo '\#include "$(notdir $<)"' > dts/$(ARCH)/$(notdir $<)_pre_compiled ; \
-	if test -e $(PROJECT_BASE)/$(BOARD_NAME).overlay; then \
+	if test -e $(DTS_OVERLAY); then \
 		echo '\#include "$(BOARD_NAME).overlay"' >> dts/$(ARCH)/$(notdir $<)_pre_compiled ; \
 	fi ; \
 	$(CPP) $(dtc_cpp_flags) -x assembler-with-cpp -o $(dtc-tmp) dts/$(ARCH)/$(notdir $<)_pre_compiled ; \
@@ -296,7 +298,7 @@ cmd_dtc = echo '\#include "$(notdir $<)"' > dts/$(ARCH)/$(notdir $<)_pre_compile
 $(obj)/%.dtb: $(src)/%.dts FORCE
 	$(call if_changed_dep,dtc)
 
-$(obj)/%.dts_compiled: $(src)/%.dts FORCE
+$(obj)/%.dts_compiled: $(src)/%.dts $(DTS_OVERLAY) FORCE
 	$(call if_changed_dep,dtc)
 
 dtc-tmp = $(subst $(comma),_,$(dot-target).dts.tmp)