npcx: Set hex_file automatically w/ npcx hex image

When using CONFIG_NPCX_IMAGE_OUTPUT_HEX, set the hex_file
runners_yaml_props_target property, so that west flash will flash the
correct file.

Change the cmake flash rules to populate the hex_file value in the
runners.yaml file if either CONFIG_BUILD_OUTPUT_HEX is enabled or some
cmake file set the runners_yaml_props_target hex_file property.

Update the npcx9m6f_evb instructions now that the filename is implicit.

Signed-off-by: Jeremy Bettis <jbettis@google.com>

boards/arm/npcx9m6f_evb/doc/index.rst

@@ -118,8 +118,7 @@ Build and flash the blinky sample.::
 
   west build -t clean && \
     west build -c -p auto -b npcx9m6f_evb samples/basic/blinky && \
-    west flash --hex-file build/zephyr/zephyr.npcx.hex \
-      --openocd /usr/local/bin/openocd --openocd-search /usr/local/share/openocd/scripts
+    west flash --openocd /usr/local/bin/openocd
 
 Debugging
 =========

cmake/flash/CMakeLists.txt

@@ -38,6 +38,10 @@ function(runners_yaml_append_config)
   runners_yaml_append("  elf_file: ${elf}")
   if(CONFIG_BUILD_OUTPUT_HEX)
     get_runners_prop(hex_file hex "${KERNEL_HEX_NAME}")
+  else()
+    get_runners_prop(hex_file hex "")
+  endif()
+  if(hex)
     runners_yaml_append("  hex_file: ${hex}")
   endif()
   if(CONFIG_BUILD_OUTPUT_BIN)

soc/arm/nuvoton_npcx/common/CMakeLists.txt

@@ -32,6 +32,8 @@ if (DEFINED CONFIG_NPCX_IMAGE_OUTPUT_BIN)
   )
   if (DEFINED CONFIG_NPCX_IMAGE_OUTPUT_HEX)
     set(NPCX_HEX_NAME ${CONFIG_KERNEL_BIN_NAME}.npcx.hex)
+    # Property magic which makes west flash choose right file.
+    set_property(TARGET runners_yaml_props_target PROPERTY hex_file "${CONFIG_KERNEL_BIN_NAME}.npcx.hex")
     set_property(GLOBAL APPEND PROPERTY extra_post_build_commands
     COMMAND $<TARGET_PROPERTY:bintools,elfconvert_command>
             $<TARGET_PROPERTY:bintools,elfconvert_flag>