ExternalProject: Stop configure target from always appearing out-of-date

When updates are disconnected, don't depend on skip-update because that
target is always considered out of date. Depend directly on the patch target
instead because it already depends on the appropriate target regardless of
whether updates are disconnected or not. This in turn means nothing depends
on the skip-update target, so it has also been removed.

Relates: #21086

Modules/ExternalProject.cmake

@@ -747,7 +747,7 @@ control needed to implement such step-level capabilities.
 
   ``<name>`` is the same as the name passed to the original call to
   :command:`ExternalProject_Add`. The specified ``<step>`` must not be one of
-  the pre-defined steps (``mkdir``, ``download``, ``update``, ``skip-update``,
+  the pre-defined steps (``mkdir``, ``download``, ``update``,
   ``patch``, ``configure``, ``build``, ``install`` or ``test``). The supported
   options are:
 
@@ -2762,21 +2762,6 @@ Update to Mercurial >= 2.1.1.
       )"
   )
 
-  if(update_disconnected)
-    _ep_get_step_stampfile(${name} skip-update skip-update_stamp_file)
-    string(REPLACE "Performing" "Skipping" comment "${comment}")
-    ExternalProject_Add_Step(${name} skip-update
-      COMMENT ${comment}
-      ALWAYS ${always}
-      EXCLUDE_FROM_MAIN 1
-      WORKING_DIRECTORY ${work_dir}
-      DEPENDEES download
-      ${log}
-      ${uses_terminal}
-    )
-    set_property(SOURCE ${skip-update_stamp_file} PROPERTY SYMBOLIC 1)
-  endif()
-
 endfunction()
 
 
@@ -2970,13 +2955,6 @@ function(_ep_add_configure_command name)
     set(uses_terminal "")
   endif()
 
-  _ep_get_update_disconnected(update_disconnected ${name})
-  if(update_disconnected)
-    set(update_dep skip-update)
-  else()
-    set(update_dep update)
-  endif()
-
   set(__cmdQuoted)
   foreach(__item IN LISTS cmd)
     string(APPEND __cmdQuoted " [==[${__item}]==]")
@@ -2985,7 +2963,7 @@ function(_ep_add_configure_command name)
     ExternalProject_Add_Step(${name} configure
       COMMAND ${__cmdQuoted}
       WORKING_DIRECTORY \${binary_dir}
-      DEPENDEES \${update_dep} patch
+      DEPENDEES patch
       DEPENDS \${file_deps}
       ${log}
       ${uses_terminal}