Fix Windows build: Use forward slashes in vcpkg paths

[Copilot]

Windows builds failed with LNK1181: cannot open input file 'openblas.lib'. The linker couldn't find the library despite vcpkg installing it correctly to C:\vcpkg\installed\x64-windows\lib.

Root cause: Backslashes in CIBW_ENVIRONMENT_WINDOWS paths were being stripped during YAML processing, resulting in malformed paths like C:vcpkginstalledx64-windowslib passed to the compiler.

Changes

Changed all Windows path separators in .github/workflows/cibuildwheel.yml from backslashes to forward slashes:

CIBW_ENVIRONMENT_WINDOWS: |
  EASYSBA_LAPACK_LIBS=openblas
  EASYSBA_INCLUDE_DIRS=C:/vcpkg/installed/x64-windows/include
  EASYSBA_LIBRARY_DIRS=C:/vcpkg/installed/x64-windows/lib
  INCLUDE=C:/vcpkg/installed/x64-windows/include
  LIB=C:/vcpkg/installed/x64-windows/lib

Windows accepts both separators; forward slashes avoid escaping issues in YAML multiline strings.

Warning

Firewall rules blocked me from connecting to one or more addresses (expand for details)

I tried to connect to the following addresses, but was blocked by firewall rules:

• https://api.github.com/graphql
  • Triggering command: /usr/bin/gh gh pr view --json number,state,title (http block)

If you need me to access, download, or install something from one of these locations, you can either:

• Configure Actions setup steps to set up my environment, which run before the firewall is enabled
• Add the appropriate URLs or hosts to the custom allowlist in this repository's Copilot coding agent settings (admins only)

---

💡 You can make Copilot smarter by setting up custom instructions, customizing its development environment and configuring Model Context Protocol (MCP) servers. Learn more Copilot coding agent tips in the docs.

[Copilot]

Pull request overview

Updates the Windows cibuildwheel GitHub Actions workflow so OpenBLAS (installed via vcpkg) can be found reliably during wheel builds, addressing a Windows linker failure caused by path escaping/formatting.

Changes:

• Switch CIBW_ENVIRONMENT_WINDOWS vcpkg paths from backslashes to forward slashes.
• Keep the OpenBLAS/vcpkg environment variables aligned with the x64-windows vcpkg install location.

---

💡 Add Copilot custom instructions for smarter, more guided reviews. Learn how to get started.

[Copilot]

INCLUDE and LIB are being overwritten to only the vcpkg paths. This can unintentionally drop the MSVC/Windows SDK include+lib search paths depending on how the toolchain env is initialized, leading to brittle builds. Safer options are to (a) rely solely on EASYSBA_INCLUDE_DIRS/EASYSBA_LIBRARY_DIRS (setup.py already consumes these), or (b) append to the existing values (similar to PATH) instead of replacing them.

Suggested change

	INCLUDE=C:/vcpkg/installed/x64-windows/include
	LIB=C:/vcpkg/installed/x64-windows/lib
	INCLUDE=C:/vcpkg/installed/x64-windows/include;{INCLUDE}
	LIB=C:/vcpkg/installed/x64-windows/lib;{LIB}