Build: compile espree's deps to ES5 when generating site (fixes #11014)…

… (#11015)

Previously, the build process would compile ESLint's dependencies to ES5 when generating a website bundle, but not espree's dependencies. Now that espree has dependencies with ES6 code, it's necessary to also compile espree's dependencies.

Makefile.js

@@ -849,7 +849,7 @@ target.browserify = function() {
     exec(`${getBinFile("browserify")} -x espree ${TEMP_DIR}linter.js -o ${BUILD_DIR}eslint.js -s eslint --global-transform [ babelify --presets [ es2015 ] ]`);
 
     // 6. Browserify espree
-    exec(`${getBinFile("browserify")} -r espree -o ${TEMP_DIR}espree.js`);
+    exec(`${getBinFile("browserify")} -r espree -o ${TEMP_DIR}espree.js --global-transform [ babelify --presets [ es2015 ] ]`);
 
     // 7. Concatenate Babel polyfill, Espree, and ESLint files together
     cat("./node_modules/babel-polyfill/dist/polyfill.js", `${TEMP_DIR}espree.js`, `${BUILD_DIR}eslint.js`).to(`${BUILD_DIR}eslint.js`);