cmake: west: west flash dependencies in sync with CMake flash target

This commit creates a list of a phony targets for each runner, that is:
`west_flash_depends`, `west_debug_depends`, and so on.
Those targets has identical dependencies as CMake runner target.
flash, debug, debugserver, attach targets.

As example `ninja flash` correctly ensures dependencies are taken into
consideration before calling `west flash`.

Unfortunately, calling `west flash` directly would not re-run the flash
dependencies, cause `west flash` would only build the default CMake
target.

Now, `west flash` calls the phony `west_flash_depends` target, ensuring
all deps are up-to-date before flashing (unless --skip-rebuild is given)

The same is true for the other mentioned runners.

Signed-off-by: Torsten Rasmussen <Torsten.Rasmussen@nordicsemi.no>

cmake/flash/CMakeLists.txt

@@ -211,6 +211,16 @@ foreach(target flash debug debugserver attach)
       ${comment}
       USES_TERMINAL
       )
+
+    # This is an artificial target to allow west to ensure all dependencies of
+    # target is build before carrying out the actual command.
+    # This allows `west` to run just the dependencies before flashing.
+    add_custom_target(west_${target}_depends
+      COMMAND ${CMAKE_COMMAND} -E echo ""
+      DEPENDS ${RUNNERS_DEPS}
+              $<TARGET_PROPERTY:zephyr_property_target,${TARGET_UPPER}_DEPENDENCIES>
+      USES_TERMINAL
+      )
   else()
     add_custom_target(${target}
       COMMAND ${CMAKE_COMMAND} -E echo \"West was not found in path. To support

scripts/west_commands/run_common.py

@@ -258,8 +258,9 @@ def load_cmake_cache(build_dir, args):
 
 def rebuild(command, build_dir, args):
     _banner(f'west {command.name}: rebuilding')
+    extra_args = ['--target', 'west_' + command.name + '_depends']
     try:
-        zcmake.run_build(build_dir)
+        zcmake.run_build(build_dir, extra_args=extra_args)
     except CalledProcessError:
         if args.build_dir:
             log.die(f're-build in {args.build_dir} failed')