macOS: Auto detection of executable path when CHROME_PATH has pointed `.app` folder

[yhatt]

For setting custom Chrome path, CHROME_PATH environment value requires the path for an executable binary.

In macOS, a common mistake is setting the path for the app /Applications/Google Chrome.app. xxx.app is actually a special directory, not an executable file. A user should set /Applications/Google Chrome.app/Contents/MacOS/Google Chrome instead.

Having said that, the detail of .app is hidden to OS users unless an explicit action. It's natural to think users that setting /Applications/Google Chrome.app is working well.

So it's helpful to provide auto-detection of executable path for macOS when filled all following conditions:

• os.platform() is 'darwin'.
• CHROME_PATH env has been set a string that has an ending .app + optional trailing slash.
• (await fsPromise.stat(env.CHROME_PATH)).isDirectory() is true.

For example, /foo/bar/ABCDEF.app will resolve as /foo/bar/ABCDEF.app/Contents/MacOS/ABCDEF.

We may have to check ./Contents/Info.plist to detect whether CFBundlePackageType is AAPL for more strict detection.