fix: disable LTO/ThinLTO in binding.gyp for Windows + Node 26 builds

Node.js 26 was built with clang-cl + lld and ThinLTO enabled. Its
installed common.gypi propagates `enable_thin_lto=true` to downstream
native addons, and the conditions inside common.gypi append
`-flto=thin` to cl.exe's AdditionalOptions and `/opt:lldltojobs=<n>`
to link.exe's AdditionalOptions whenever that variable is true.

That's fine when the addon is also built with clang-cl, but the
overwhelmingly common case for consumers is the regular MSVC toolchain
where:

  - cl.exe warns and ignores `-flto=thin` (D9002)
  - link.exe warns and ignores `/flto=thin` (LNK4044)
  - link.exe fails with `LNK1117: syntax error in option
    'opt:lldltojobs=2'` because /OPT: only accepts
    REF/ICF/NOREF/NOICF/LBR/NOLBR

Force enable_lto and enable_thin_lto off in binding.gyp's `variables`
so the common.gypi conditions evaluate false and the flags are never
emitted. Affects every consumer building node-libcurl from source on
Windows against Node 26; harmless on Linux/macOS and on older Node
versions.

Author: JCMais

CHANGELOG.md

@@ -9,6 +9,7 @@ and this project adheres to [Semantic Versioning](http://semver.org/spec/v2.0.0.
 ### Breaking Change
 
 ### Fixed
+- Fixed Windows source builds against Node.js 26 failing with `LINK : fatal error LNK1117: syntax error in option 'opt:lldltojobs=2'`. Node 26 was built with clang-cl + lld + ThinLTO and its installed `common.gypi` propagates `enable_thin_lto=true` to downstream addons, which then appends `-flto=thin` to `cl.exe` and `/opt:lldltojobs=<n>` to `link.exe` — both invalid for the regular MSVC toolchain. Force `enable_lto` and `enable_thin_lto` off in `binding.gyp` so those conditions evaluate to false. Affects every consumer building node-libcurl from source on Windows + Node 26.
 
 ### Added
 

binding.gyp

@@ -14,7 +14,22 @@
     'node_libcurl_debug%': 'false',
     'node_libcurl_asan_debug%': 'false',
     'node_libcurl_cpp_std%': 'c++20',
-    'macos_universal_build%': 'false'
+    'macos_universal_build%': 'false',
+    # Node.js 26 was built with clang-cl + lld and ThinLTO enabled, and
+    # its installed common.gypi propagates `enable_thin_lto=true` to
+    # downstream native addons. When the addon is then built with the
+    # regular MSVC toolchain (the overwhelmingly common case for
+    # consumers), the conditions inside common.gypi append `-flto=thin`
+    # to cl.exe's AdditionalOptions and `/opt:lldltojobs=<n>` to
+    # link.exe's AdditionalOptions. cl.exe warns and ignores `-flto=thin`,
+    # but link.exe bails with `LNK1117: syntax error in option` on the
+    # bogus `/OPT:lldltojobs=` value (link.exe's /OPT: only takes
+    # REF/ICF/NOREF/NOICF/LBR/NOLBR). Force these off so the conditions
+    # evaluate false and the flags are never emitted. Affects every
+    # consumer trying to build node-libcurl from source against Node 26
+    # on Windows; harmless everywhere else.
+    'enable_lto': 'false',
+    'enable_thin_lto': 'false',
   },
   'targets': [
     {