nyc.config.js: Also set custom value for temp-dir option

It enables to modify another code coverage output directory when running
cypress tests in parallel and thus avoid race conditions when multiple
cypress processes try to write to the same coverage output file.

.gitignore

@@ -33,7 +33,7 @@ dist/
 package-lock.json
 yarn-error.log
 cypress/mochawesome/
-.nyc_output/
+.nyc_output*/
 cypress/coverage*/
 cypress/fixtures/source*.json
 cypress/junit/

nyc.config.js

 'use strict';
 
 let reportDir = 'cypress/coverage';
+let tempDir = '.nyc_output';
 const parallelBuildId = process.env.CYPRESS_PARALLEL_BUILD_ID;
 if (parallelBuildId !== undefined) {
   reportDir += parallelBuildId;
+  tempDir += parallelBuildId;
 }
 
 module.exports = {
@@ -11,5 +13,6 @@ module.exports = {
     'assets/src/bundles/vendors/index.js',
     'assets/src/thirdparty/**/*.js'
   ],
-  'report-dir': reportDir
+  'report-dir': reportDir,
+  'temp-dir': tempDir
 };