How to change the Xcode version in GitHub Actions

Change Xcode version in GitHub Actions

# Change Xcode version in GitHub Actions

As of today (2019-08-21) I haven't found any documentation on changing Xcode versions when
using GitHub actions. So I checked the applications folder and everything we need is 
already there. 🤩

```
> ls -n /Applications/ | grep Xcode*
lrwxr-xr-x   1 0    80    30 Aug  2 19:31 Xcode.app -> /Applications/Xcode_10.2.1.app
drwxr-xr-x   3 501  20    96 Oct 20  2018 Xcode_10.1.app
lrwxr-xr-x   1 501  80    28 Aug  2 18:19 Xcode_10.1_beta.app -> /Applications/Xcode_10.1.app
drwxr-xr-x   3 501  20    96 Apr  6 00:33 Xcode_10.2.1.app
lrwxr-xr-x   1 501  80    30 Aug  2 18:47 Xcode_10.2.1_beta.app -> /Applications/Xcode_10.2.1.app
drwxr-xr-x   3 501  20    96 Mar 18 02:39 Xcode_10.2.app
lrwxr-xr-x   1 501  80    28 Aug  2 18:33 Xcode_10.2_beta.app -> /Applications/Xcode_10.2.app
drwxr-xr-x   3 501  20    96 Jul 13 04:47 Xcode_10.3.app
lrwxr-xr-x   1 501  80    28 Aug  2 19:01 Xcode_10.3_beta.app -> /Applications/Xcode_10.3.app
drwxr-xr-x   3 501  20    96 Sep 11  2018 Xcode_10.app
lrwxr-xr-x   1 501  80    26 Aug  2 18:05 Xcode_10_beta.app -> /Applications/Xcode_10.app
lrwxr-xr-x   1 501  80    31 Aug  2 19:16 Xcode_11.app -> /Applications/Xcode_11_beta.app
drwxr-xr-x   3 501  20    96 Jul 26 16:51 Xcode_11_beta.app
drwxr-xr-x   3 501  20    96 Jun  5  2018 Xcode_9.4.1.app
```

Therefore switching the build tools with

```
> sudo xcode-select -s /Applications/Xcode_11.app/Contents/Developer
```

is not a problem. Please note that sudo is required for this operation.