tools: generate template literal for addon tests

Instead of generating string concatenation, generate a template literal.
This is mostly useful as a pre-emptive measure for avoiding problems
when (if?) we enable the prefer-template lint rule in the test
directory.

tools/doc/addon-verify.js

@@ -66,7 +66,10 @@ function verifyFiles(files, blockName, onprogress, ondone) {
     if (name === 'test.js') {
       files[name] = `'use strict';
 const common = require('../../common');
-${files[name].replace('Release', "' + common.buildType + '")}
+${files[name].replace(
+    "'./build/Release/addon'",
+    // eslint-disable-next-line no-template-curly-in-string
+    '`./build/${common.buildType}/addon`')}
 `;
     }
     return {