Handle line endings correctly on Windows in build script for RN (#26727)

## Summary

We added some post-processing in the build for RN in #26616 that broke
for users on Windows due to how line endings were handled to the regular
expression to insert some directives in the docblock. This fixes that
problem, reported in #26697 as well.

## How did you test this change?

Verified files are still built correctly on Mac/Linux. Will ask for help
to test on Windows.

DiffTrain build for [f87e97a](f87e97a)

Author: josephsavona

compiled/facebook-www/REVISION

@@ -1 +1 @@
-ded4a785b875d384f78efa28279550d86d93f54f
+f87e97a0a67fa7cfd7e6f2ec985621c0e825cb23

compiled/facebook-www/React-dev.modern.js

@@ -27,7 +27,7 @@ if (
 }
           "use strict";
 
-var ReactVersion = "18.3.0-www-modern-95e6ae95";
+var ReactVersion = "18.3.0-www-modern-bcc00dd5";
 
 // ATTENTION
 // When adding new symbols to this file,