ExternalProject: Quote each git --config option to handle spaces

Fixes: #20354

Modules/ExternalProject.cmake

@@ -1096,7 +1096,7 @@ function(_ep_write_gitclone_script script_filename source_dir git_EXECUTABLE git
     list(APPEND git_clone_options --progress)
   endif()
   foreach(config IN LISTS git_config)
-    list(APPEND git_clone_options --config ${config})
+    list(APPEND git_clone_options --config \"${config}\")
   endforeach()
   if(NOT ${git_remote_name} STREQUAL "origin")
     list(APPEND git_clone_options --origin \"${git_remote_name}\")

Tests/ExternalProject/CMakeLists.txt

@@ -380,7 +380,9 @@ if(do_git_tests)
     set(proj TutorialStep1-GIT-config)
     ExternalProject_Add(${proj}
       GIT_REPOSITORY "${local_git_repo}"
-      GIT_CONFIG core.eol=lf core.autocrlf=input
+      GIT_CONFIG core.eol=lf
+                 core.autocrlf=input
+                 "http.extraheader=AUTHORIZATION: bearer --unsupportedOption"
       CMAKE_GENERATOR "${CMAKE_GENERATOR}"
       CMAKE_ARGS -DCMAKE_INSTALL_PREFIX:PATH=<INSTALL_DIR>
       INSTALL_COMMAND ""