cmake: Fix invocation of add_custom_command()

Fixes: zephyrproject-rtos/zephyr#79295

Fix invocation of add_custom_command() by correcting the wrong
`CMAKE_EXECUTABLE` variable to the correct `CMAKE_COMMAND` variable name
and added `-E` to correctly set up the environment.

Export ZEPHYR_BASE when invoking the custom command to ensure that the
ZEPHYR_BASE used by CMake is also the value used when invoking the
build.

Signed-off-by: Torsten Rasmussen <[email protected]>

Author: tejlmand

CMakeLists.txt

@@ -143,8 +143,9 @@ ${config_paths}
     OUTPUT ${DUMMY_FILE}
     BYPRODUCTS ${RUST_LIBRARY} ${WRAPPER_FILE}
     COMMAND
-      ${CMAKE_EXECUTABLE}
+      ${CMAKE_COMMAND} -E
       env BUILD_DIR=${CMAKE_CURRENT_BINARY_DIR}
+      ZEPHYR_BASE=${ZEPHYR_BASE}
       DOTCONFIG=${DOTCONFIG}
       ZEPHYR_DTS=${ZEPHYR_DTS}
       INCLUDE_DIRS="${include_dirs}"