scripts: west sign supports signing for external NOR flash memory

west sign accepts signing image when built and linked for
an external NOR memory (which has no write-block size property)

Signed-off-by: Francois Ramu <[email protected]>

Author: FRASTM

scripts/west_commands/sign.py

@@ -397,9 +397,12 @@ def edt_flash_params(flash):
 
         # Die on missing or zero alignment or slot_size.
         if "write-block-size" not in flash.props:
-            log.die('DT zephyr,flash node has no write-block-size;',
-                    "can't determine imgtool write alignment")
-        align = flash.props['write-block-size'].val
+#            log.die('DT zephyr,flash node has no write-block-size;',
+#                    "can't determine imgtool write alignment")
+            align=4
+        else:
+            align = flash.props['write-block-size'].val
+
         if align == 0:
             log.die('expected nonzero flash alignment, but got '
                     'DT flash device write-block-size {}'.format(align))