Use a response file for stdlib sources

The experimental stdlib runtime build has several sources files,
resulting in an absolutely massive commandline. This seems to be
approaching, or passing, the maximum command line length on Windows.
Switch the Windows build to use a response file generated by CMake to
pass the source files to the compiler.

Author: etcwilde

utils/build.ps1

@@ -2338,6 +2338,7 @@ function Build-ExperimentalRuntime {
         CMAKE_Swift_COMPILER_WORKS = "YES";
         CMAKE_STATIC_LIBRARY_PREFIX_Swift = "lib";
         CMAKE_SYSTEM_NAME = $Platform.OS.ToString();
+        CMAKE_NINJA_FORCE_RESPONSE_FILE = "YES";
 
         # NOTE(compnerd) we can get away with this currently because we only
         # use the C portion of the dispatch build, which is always built