MSVC: Add /FS flag for cl >= 18 to allow parallel compilation (#14492)

In generators such as Ninja that can run multiple "cl" processes that
refer to the same compiler .pdb file (/Fd) at the same time, MSVC from
Visual Studio 2013 complains:

 fatal error C1041: cannot open program database '.../vc120.pdb';
 if multiple CL.EXE write to the same .PDB file, please use /FS

According to "cl /?":

 /FS force to use MSPDBSRV.EXE

Add the flag to compilation lines for this compiler version just after the
/Fd option.

Modules/Platform/Windows-MSVC-C.cmake

@@ -1,2 +1,5 @@
 include(Platform/Windows-MSVC)
+if(NOT CMAKE_C_COMPILER_VERSION VERSION_LESS 18.0)
+  set(_FS_C " /FS")
+endif()
 __windows_compiler_msvc(C)

Modules/Platform/Windows-MSVC-CXX.cmake

@@ -1,3 +1,6 @@
 include(Platform/Windows-MSVC)
 set(_COMPILE_CXX " /TP")
+if(NOT CMAKE_CXX_COMPILER_VERSION VERSION_LESS 18.0)
+  set(_FS_CXX " /FS")
+endif()
 __windows_compiler_msvc(CXX)

Modules/Platform/Windows-MSVC.cmake

@@ -232,7 +232,7 @@ macro(__windows_compiler_msvc lang)
   set(CMAKE_${lang}_CREATE_STATIC_LIBRARY  "<CMAKE_LINKER> /lib ${CMAKE_CL_NOLOGO} <LINK_FLAGS> /out:<TARGET> <OBJECTS> ")
 
   set(CMAKE_${lang}_COMPILE_OBJECT
-    "<CMAKE_${lang}_COMPILER> ${CMAKE_START_TEMP_FILE} ${CMAKE_CL_NOLOGO}${_COMPILE_${lang}} <FLAGS> <DEFINES> /Fo<OBJECT> /Fd<OBJECT_DIR>/ -c <SOURCE>${CMAKE_END_TEMP_FILE}")
+    "<CMAKE_${lang}_COMPILER> ${CMAKE_START_TEMP_FILE} ${CMAKE_CL_NOLOGO}${_COMPILE_${lang}} <FLAGS> <DEFINES> /Fo<OBJECT> /Fd<OBJECT_DIR>/${_FS_${lang}} -c <SOURCE>${CMAKE_END_TEMP_FILE}")
   set(CMAKE_${lang}_CREATE_PREPROCESSED_SOURCE
     "<CMAKE_${lang}_COMPILER> > <PREPROCESSED_SOURCE> ${CMAKE_START_TEMP_FILE} ${CMAKE_CL_NOLOGO}${_COMPILE_${lang}} <FLAGS> <DEFINES> -E <SOURCE>${CMAKE_END_TEMP_FILE}")
   set(CMAKE_${lang}_CREATE_ASSEMBLY_SOURCE