[SR-13213] Building 5.3 sort of required 5.3…?

[swift-ci]

Previous ID	SR-13213
Radar	None
Original Reporter	griotspeak (JIRA User)
Type	Bug

Additional Detail from JIRA

Votes	0
Component/s
Labels	Bug, build
Assignee	None
Priority	Medium

md5: 9262d7797f19d015d8d1592a113d6e30

Issue Description:

I checked out bf47403162fc53281f242da50649fda5b9a193f5 and could not build it with Xcode 11.4 using the 5.2.4 toolchain. I ended up needing to use Xcode 12 beta to successfully build.

The failure I encountered was an issue with building the AppKit overlay. error: no such module '_SwiftAppKitOverlayShims'

[MaxDesiatov]

Building the `main` branch usually requires the latest beta version of Xcode, which is documented in the macOS requirements section.