Fix Windows cibuildwheel failure: linker cannot find openblas.lib

[Copilot]

Windows builds were failing with LNK1181: cannot open input file 'openblas.lib'. Environment variables for library paths defined in workflow YAML were not propagating to cibuildwheel's isolated build environment.

Changes

• Moved Windows configuration to pyproject.toml: CIBW_BEFORE_ALL_WINDOWS and CIBW_ENVIRONMENT_WINDOWS now defined in [tool.cibuildwheel.windows] section where cibuildwheel correctly passes them to the build
• Added library path environment variables: EASYSBA_INCLUDE_DIRS and EASYSBA_LIBRARY_DIRS point to vcpkg's x64-windows installation paths
• PowerShell-based vcpkg setup: Conditional check for existing vcpkg installation before clone/bootstrap
• Enhanced caching: Hash-based cache key with restore-keys for vcpkg artifacts

Configuration

[tool.cibuildwheel.windows]
before-all = "powershell -Command \"if (!(Test-Path C:\\vcpkg\\vcpkg.exe)) { git clone https://github.com/microsoft/vcpkg.git C:\\vcpkg; C:\\vcpkg\\bootstrap-vcpkg.bat -disableMetrics }; C:\\vcpkg\\vcpkg.exe install openblas:x64-windows\""
environment = { 
  EASYSBA_LAPACK_LIBS = "openblas", 
  EASYSBA_INCLUDE_DIRS = "C:\\vcpkg\\installed\\x64-windows\\include", 
  EASYSBA_LIBRARY_DIRS = "C:\\vcpkg\\installed\\x64-windows\\lib" 
}

The setup.py already parses these environment variables via _parse_path_env() and adds them to library_dirs for the Extension.

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Pull request overview

This PR fixes Windows cibuildwheel failures caused by the linker being unable to locate openblas.lib. The root issue was that environment variables defined in the GitHub Actions workflow YAML were not propagating to cibuildwheel's isolated build environment.

Changes:

• Relocated Windows-specific cibuildwheel configuration from workflow YAML to pyproject.toml
• Added library and include path environment variables pointing to vcpkg installation directories
• Enhanced vcpkg caching with hash-based keys and restore fallbacks

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated no comments.

File	Description
pyproject.toml	Added Windows cibuildwheel configuration with vcpkg setup command and environment variables for library/include paths
.github/workflows/cibuildwheel.yml	Removed Windows environment variables from workflow and improved vcpkg cache configuration

Comments suppressed due to low confidence (2)

pyproject.toml:32

• The command string uses semicolons to chain PowerShell commands, which can fail silently if any intermediate command fails. Consider using -ErrorAction Stop and separating commands with && or properly handling errors to ensure the vcpkg installation doesn't proceed if cloning or bootstrapping fails.

before-all = "powershell -Command \"if (!(Test-Path C:\\vcpkg\\vcpkg.exe)) { git clone https://github.com/microsoft/vcpkg.git C:\\vcpkg; C:\\vcpkg\\bootstrap-vcpkg.bat -disableMetrics }; C:\\vcpkg\\vcpkg.exe install openblas:x64-windows\""

pyproject.toml:33

• The hardcoded paths C:\\vcpkg\\installed\\x64-windows\\include and C:\\vcpkg\\installed\\x64-windows\\lib are duplicated from the before-all command and tightly couple the configuration to this specific installation location. Consider using a variable or ensuring consistency if the vcpkg path ever needs to change.

environment = { EASYSBA_LAPACK_LIBS = "openblas", EASYSBA_INCLUDE_DIRS = "C:\\vcpkg\\installed\\x64-windows\\include", EASYSBA_LIBRARY_DIRS = "C:\\vcpkg\\installed\\x64-windows\\lib" }

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