feat(ci): upgrade python and remove LLVM LTO flags from MSVC build to fix Node 26 Windows CI by styfle · Pull Request #1330 · vercel/ncc (original) (raw)

Root Cause

Node.js 26 on Windows is compiled using Clang with thin LTO enabled (enable_thin_lto=true, lto_jobs=2). When node-gyp rebuild runs without --nodedir, it generates build/config.gypi from the running Node.js binary's process.config. This causes Node.js's common.gypi to inject LLVM/Clang-specific flags into the MSVC build:

• -flto=thin → compiler/linker warning (ignored by MSVC)
• /opt:lldltojobs=2 → fatal linker error LNK1117 (MSVC does not understand LLVM LTO job flags)

Fix

Modified test/binary/binding.gyp to strip the incompatible LLVM LTO flags when building on Windows with MSVC:

• Added a "lto_jobs%": "" default variable as a safe fallback for Node versions that do not define this variable
• Added a Windows-specific conditions block using GYP's AdditionalOptions! list-removal operator to remove -flto=thin, -flto=full, and /opt:lldltojobs=<(lto_jobs) from both VCCLCompilerTool and VCLinkerTool options

The fix is a no-op on Node 22/24 (LTO not enabled, no flags to remove) and does not affect Linux or macOS builds.