cmake: add_llext_target: fix command expansion

This fixes the invocation of the 'elfconvert' and 'slid_inject' commands
in the `add_llext_target` function by ensuring that the arguments are
expanded correctly before passing them to the shell.

Signed-off-by: Luca Burelli <l.burelli@arduino.cc>

cmake/modules/extensions.cmake

@@ -5960,6 +5960,7 @@ function(add_llext_target target_name)
             $<TARGET_PROPERTY:bintools,elfconvert_flag_final>
     COMMAND ${slid_inject_cmd}
     DEPENDS ${llext_proc_target} ${llext_pkg_input}
+    COMMAND_EXPAND_LISTS
   )
 
   # Add user-visible target and dependency, and fill in properties