do not try creating reports on legacy Node.js

bin/c8.js

@@ -21,14 +21,17 @@ async function run () {
   ].indexOf(argv._[0]) !== -1) {
     argv = buildYargs(true).parse(process.argv.slice(2))
   } else {
+    // allow c8 to run on Node 8 (coverage just won't work).
+    if (!promises) {
+      foreground(hideInstrumenterArgs(argv))
+      return
+    }
+
     if (argv.clean) {
       await promisify(rimraf)(argv.tempDirectory)
     }
-    // allow c8 to run on Node 8 (coverage just won't work).
-    if (promises) {
-      await promises.mkdir(argv.tempDirectory, { recursive: true })
-    }
 
+    await promises.mkdir(argv.tempDirectory, { recursive: true })
     process.env.NODE_V8_COVERAGE = argv.tempDirectory
     foreground(hideInstrumenterArgs(argv), async (done) => {
       try {

test/legacy-node.js

@@ -1,20 +1,21 @@
 /* global describe, it */
 
 const { execFile } = require('child_process')
-const { mkdir } = require('fs').promises
+const { existsSync } = require('fs')
 const { join } = require('path')
 const { promisify } = require('util')
 const c8Path = require.resolve('./fixtures/disable-fs-promises')
 const nodePath = process.execPath
 
 describe('c8 on Node.js < 10', () => {
   it('doesn\'t crash', async () => {
-    await mkdir(join(__dirname, '..', 'tmp', 'legacy-nodejs'))
     await promisify(execFile)(nodePath, [
       c8Path,
       '--temp-directory=tmp/legacy-nodejs',
       'node',
       '--version'
     ])
+
+    existsSync(join(__dirname, '..', 'tmp', 'legacy-nodejs')).should.equal(false)
   })
 })