clear cache between builds

Author: lobsterkatie

rollup.config.js

@@ -94,6 +94,10 @@ export function makeBaseBundleConfig(options) {
       },
     },
     include: ['*.ts+(|x)', '**/*.ts+(|x)', '../**/*.ts+(|x)'],
+    // the typescript plugin doesn't handle concurrency very well, so clean the cache between builds and don't complain
+    // when old cache files can't be found (see https://github.com/ezolenko/rollup-plugin-typescript2/issues/15)
+    clean: true,
+    verbosity: 0,
   };
 
   const typescriptPluginES5 = typescript(