Add option(CMake_VERSION_NO_GIT) for broken Git or slow filesystem

Help inform user in GUI that it's possible to build CMake without Git.
This is useful for Git on Windows Subsystem for Linux or other platforms
where filesystem access for Git is very slow or Git program is broken.

Fixes: #28051

CMakeLists.txt

@@ -442,6 +442,10 @@ if(NOT CMake_TEST_EXTERNAL_CMAKE)
   endif()
 endif()
 
+if(EXISTS "${CMAKE_CURRENT_LIST_DIR}/.git")
+  option(CMake_VERSION_NO_GIT "Do not attempt to determine CMake version from Git" OFF)
+endif()
+
 #-----------------------------------------------------------------------
 # The main section of the CMakeLists file
 #