cmake: Allow specifying custom VERSION file dependency

Allows applications and projects to specify their own requirements
for the application VERSION file to be re-generated, this fixes an
issue whereby the application git repository is updated with a new
commit but the old commit is still used by a build, users would
need to add a dependency in their application to the git index file

Signed-off-by: Jamie McCrae <jamie.mccrae@nordicsemi.no>

Author: nordicjm

CMakeLists.txt

@@ -737,6 +737,10 @@ zephyr_get(KERNEL_VERSION_CUSTOMIZATION SYSBUILD LOCAL)
 set_property(TARGET version_h PROPERTY KERNEL_VERSION_CUSTOMIZATION ${KERNEL_VERSION_CUSTOMIZATION})
 
 if(EXISTS ${APPLICATION_SOURCE_DIR}/VERSION)
+  # A generator expression is used to allow applications to add their own dependencies for the
+  # file version, this might typically be the git index file if the application is in a git
+  # repository. To add a dependency to the application version file, this can be used:
+  # set_property(TARGET app_version_h PROPERTY APP_VERSION_DEPENDS <FILE>)
   add_custom_command(
     OUTPUT ${PROJECT_BINARY_DIR}/include/generated/zephyr/app_version.h
     COMMAND ${CMAKE_COMMAND} -DZEPHYR_BASE=${ZEPHYR_BASE}
@@ -747,6 +751,7 @@ if(EXISTS ${APPLICATION_SOURCE_DIR}/VERSION)
       ${build_version_argument}
       -P ${ZEPHYR_BASE}/cmake/gen_version_h.cmake
     DEPENDS ${APPLICATION_SOURCE_DIR}/VERSION ${git_dependency}
+      $<TARGET_PROPERTY:app_version_h,APP_VERSION_DEPENDS>
     COMMAND_EXPAND_LISTS
   )
   add_custom_target(