Allow watching workspaces at /tmp/some-dir

[oxalica]

See #4616 (comment)

[oxalica]

After fixed isValidWatchRoot tests, this error still occur. I have no idea what's going wrong here.

  ● fileSystemWatcher › should watch for file create

    excess data found after input buffer, use BunserBuf instead

      75 |     client = c
      76 |     c.on('data', data => {
    > 77 |       let obj = bser.loadFromBuffer(data)
         |                      ^
      78 |       if (obj[0] == 'watch-project') {
      79 |         sendResponse(watchResponse || { watch: obj[1], warning: 'warning' })
      80 |       } else if (obj[0] == 'unsubscribe') {

      at Object.Error [as loadFromBuffer] (node_modules/bser/index.js:439:11)
      at Socket.loadFromBuffer (src/__tests__/core/fileSystemWatcher.test.ts:77:22)

[fannheyward]

Will check the failed tests ASAP.

[fannheyward]

The failed test is related with should use relative pattern #3, after this test, should watch for file create is broken.