binman: Add a way to enable debugging from the build

When the build fails due to something wrong in binman it is sometimes
useful to get a full backtrace showing the location of the failure. Add
a BINMAN_DEBUG environment variable to support this along with some
documentation.
Signed-off-by: NSimon Glass <sjg@chromium.org>

Makefile

@@ -1048,9 +1048,11 @@ u-boot.ldr:	u-boot
 
 # binman
 # ---------------------------------------------------------------------------
+# Use 'make BINMAN_DEBUG=1' to enable debugging
 quiet_cmd_binman = BINMAN  $@
-cmd_binman = $(srctree)/tools/binman/binman -d u-boot.dtb -O . \
-		-I . -I $(srctree)/board/$(BOARDDIR) $<
+cmd_binman = $(srctree)/tools/binman/binman -u -d u-boot.dtb -O . -m \
+		-I . -I $(srctree) -I $(srctree)/board/$(BOARDDIR) \
+		$(if $(BINMAN_DEBUG),-D) $(BINMAN_$(@F)) $<
 
 OBJCOPYFLAGS_u-boot.ldr.hex := -I binary -O ihex
 

tools/binman/README

@@ -723,6 +723,12 @@ If you need to specify a particular device-tree compiler to use, you can define
 the DTC environment variable. This can be useful when the system dtc is too
 old.
 
+To enable a full backtrace and other debugging features in binman, pass
+BINMAN_DEBUG=1 to your build:
+
+   make sandbox_defconfig
+   make BINMAN_DEBUG=1
+
 
 History / Credits
 -----------------