Execute `yarn --ignore-engines` for extensions

build/npm/postinstall.js

@@ -21,6 +21,10 @@ function yarnInstall(location, opts) {
 	const argv = JSON.parse(raw);
 	const original = argv.original || [];
 	const args = original.filter(arg => arg === '--ignore-optional' || arg === '--frozen-lockfile');
+	if (opts.ignoreEngines) {
+		args.push('--ignore-engines');
+		delete opts.ignoreEngines;
+	}
 
 	console.log(`Installing dependencies in ${location}...`);
 	console.log(`$ yarn ${args.join(' ')}`);
@@ -53,7 +57,7 @@ const extensions = allExtensionFolders.filter(e => {
 	}
 });
 
-extensions.forEach(extension => yarnInstall(`extensions/${extension}`));
+extensions.forEach(extension => yarnInstall(`extensions/${extension}`, { ignoreEngines: true }));
 
 function yarnInstallBuildDependencies() {
 	// make sure we install the deps of build/lib/watch for the system installed