cmake: remove GIT_CHANGED_SOURCES (#24737)

dead code

cmake/tools/SetupGit.cmake

@@ -4,41 +4,9 @@ find_command(
   COMMAND
     git
   REQUIRED
-    OFF
+    ${CI}
 )
 
 if(NOT GIT_PROGRAM)
   return()
 endif()
-
-set(GIT_DIFF_COMMAND ${GIT_PROGRAM} diff --no-color --name-only --diff-filter=AMCR origin/main HEAD)
-
-execute_process(
-  COMMAND
-    ${GIT_DIFF_COMMAND}
-  WORKING_DIRECTORY
-    ${CWD}
-  OUTPUT_STRIP_TRAILING_WHITESPACE
-  OUTPUT_VARIABLE
-    GIT_DIFF
-  ERROR_STRIP_TRAILING_WHITESPACE
-  ERROR_VARIABLE
-    GIT_DIFF_ERROR
-  RESULT_VARIABLE
-    GIT_DIFF_RESULT
-)
-
-if(NOT GIT_DIFF_RESULT EQUAL 0)
-  message(WARNING "Command failed: ${GIT_DIFF_COMMAND} ${GIT_DIFF_ERROR}")
-  return()
-endif()
-
-string(REPLACE "\n" ";" GIT_CHANGED_SOURCES "${GIT_DIFF}")
-
-if(CI)
-  set(GIT_CHANGED_SOURCES "${GIT_CHANGED_SOURCES}")
-  message(STATUS "Set GIT_CHANGED_SOURCES: ${GIT_CHANGED_SOURCES}")
-endif()
-
-list(TRANSFORM GIT_CHANGED_SOURCES PREPEND ${CWD}/)
-list(LENGTH GIT_CHANGED_SOURCES GIT_CHANGED_SOURCES_COUNT)