Remove Explicit Deletion of CMake /GR Flag as 3.20's *CMP0117* by Default Doesn't Add It (#96814)

* Remove /GR flag as new CMake Policy doesn't add it by default.

* Tell CMake to use the new behavior of CMP0117.

* CMake policy is by default set when not specified, so removing the
explicit setting in CMakeLists.txt

* Flag /GR- fix.

* Restored accidentally deleted comment.

Author: ivdiazsa

eng/native/configurecompiler.cmake

@@ -780,9 +780,7 @@ if (MSVC)
   add_compile_options($<$<COMPILE_LANGUAGE:C,CXX>:/GS>) # Explicitly enable the buffer security checks
   add_compile_options($<$<COMPILE_LANGUAGE:C,CXX>:/fp:precise>) # Enable precise floating point
 
-  # disable C++ RTTI
-  # /GR is added by default by CMake, so remove it manually.
-  string(REPLACE "/GR " " " CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS}")
+  # Disable C++ RTTI
   set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} /GR-")
 
   add_compile_options($<$<COMPILE_LANGUAGE:C,CXX>:/FC>) # use full pathnames in diagnostics