kbuild: Support a FIT_EXTRA_ARGS environment variable

In some cases it is useful to be able to pass additional flags to the
make_fit.py script. For example, since ramdisks are typically large,
passing -E to use external data can be helpful.

Add a new FIT_EXTRA_ARGS variable for this.

Signed-off-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Nicolas Schier <nsc@kernel.org>
Reviewed-by: Thomas Weißschuh <thomas.weissschuh@linutronix.de>
Link: https://patch.msgid.link/20260106162738.2605574-5-sjg@chromium.org
Signed-off-by: Nathan Chancellor <nathan@kernel.org>

Author: sjg20

scripts/Makefile.lib

@@ -400,7 +400,7 @@ FIT_COMPRESSION ?= gzip
 
 quiet_cmd_fit = FIT     $@
       cmd_fit = $(MAKE_FIT) -o $@ --arch $(UIMAGE_ARCH) --os linux \
-		--name '$(UIMAGE_NAME)' \
+		--name '$(UIMAGE_NAME)' $(FIT_EXTRA_ARGS) \
 		$(if $(findstring 1,$(KBUILD_VERBOSE)),-v) \
 		$(if $(FIT_DECOMPOSE_DTBS),--decompose-dtbs) \
 		--compress $(FIT_COMPRESSION) -k $< @$(word 2,$^)