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

Summary:
## 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 commit facebook/react@f87e97a.

Changelog: [Internal]

Reviewed By: kassens

Differential Revision: D45279164

Pulled By: rubennorte

fbshipit-source-id: 5372e8357c99bb09704715b155cb85422ec7886a

packages/react-native/Libraries/Renderer/REVISION

@@ -1 +1 @@
-25b99efe0c9c9d593c86829386c86740d409fa8c
+f87e97a0a67fa7cfd7e6f2ec985621c0e825cb23