Use copies for versioned names on Windows

Versioned UNIX libraries and executables produce multiple names for a
single target using one of

  cmake -E cmake_symlink_library
  cmake -E cmake_symlink_executable

to create symlinks to the real file for the extra names.  However, when
cross-compiling from Windows to Linux we cannot create symlinks.  This
commit teaches CMake to make copies instead of symbolic links when
running on windows.  While this approach does not produce exactly what
Linux wants to see, at least the build will complete and the binary will
run on the target system.  See issue #9171.

Source/cmake.cxx

@@ -3129,8 +3129,12 @@ bool cmake::SymlinkInternal(std::string const& file, std::string const& link)
     {
     cmSystemTools::RemoveFile(link.c_str());
     }
+#if defined(_WIN32) && !defined(__CYGWIN__)
+  return cmSystemTools::CopyFileAlways(file.c_str(), link.c_str());
+#else
   std::string linktext = cmSystemTools::GetFilenameName(file);
   return cmSystemTools::CreateSymlink(linktext.c_str(), link.c_str());
+#endif
 }
 
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