fix: emit Windows batch launchers with CRLF line endings

[titusfortner]

Problem

• On Windows, rb_binary/rb_test intermittently failed with The system cannot find the batch label specified - rlocation, breaking runfiles lookups (rlocation, require 'bazel/runfiles'). Linux and macOS were unaffected.
• Root cause is line endings, not batch logic: the generated .cmd launcher is LF-only, and cmd.exe seeks goto/call :label targets by byte offset — a scan that is unreliable on LF-only files. Failures were non-deterministic (whether a label straddled an internal read-buffer boundary), which is the signature of this bug rather than a code error.

Solution

• Emit the generated .cmd with CRLF throughout. It's assembled from two pieces, so both are handled: the *.cmd.tpl templates are pinned to CRLF via .gitattributes, and the batch code injected from Starlark is normalized to CRLF.
• The .gitattributes pin isn't dev-only. The same CRLF conversion is applied when the release archive is built, so consumers get the fixed launchers whether they depend on rules_ruby via BCR, an archive, or git.

Receipts

Downstream Selenium Windows CI, same target set, with an override onto this branch (SeleniumHQ/selenium@9e400e6):

• Before: 22/51 rb_test targets fail at require 'bazel/runfiles' (non-deterministic across identical targets on one machine).
• After: all green.