Bump C++ standard to C++20 for Node 24+

Author: dmartin-figma

utils/defaultCxxStandard.js

@@ -1,18 +1,21 @@
 const targetSpecified = process.argv[2] !== 'none';
 
-let isNode18OrElectron20AndUp = false;
+let cxxStandard = '14';
 if (targetSpecified) {
   // Assume electron if target is specified.
   // If building node 18 / 19 via target, will need to specify C++ standard manually
-  const majorVersion = process.argv[2].split('.')[0];
-  isNode18OrElectron20AndUp = majorVersion >= 20;
+  const majorVersion = Number.parseInt(process.argv[2].split('.')[0]);
+  if (majorVersion >= 20) {
+    cxxStandard = '17';
+  }
 } else {
-  // Node 18 === 108
-  isNode18OrElectron20AndUp = Number.parseInt(process.versions.modules) >= 108;
+  // Node 18 === 108, Node 24 === 137 (V8 headers require C++20)
+  const moduleVersion = Number.parseInt(process.versions.modules);
+  if (moduleVersion >= 137) {
+    cxxStandard = '20';
+  } else if (moduleVersion >= 108) {
+    cxxStandard = '17';
+  }
 }
 
-const defaultCxxStandard = isNode18OrElectron20AndUp
-  ? '17'
-  : '14';
-
-process.stdout.write(defaultCxxStandard);
+process.stdout.write(cxxStandard);