[SR-13477] Cannot build toolchain with Xcode 12 beta 3 or later.

[johnno1962]

Previous ID	SR-13477
Radar	rdar://problem/68115900
Original Reporter	@johnno1962
Type	Bug

Environment

Catalina 10.15.4, Xcode 12 beta 2

Additional Detail from JIRA

Votes	0
Component/s	Compiler, LLDB for Swift
Labels	Bug
Assignee	None
Priority	Medium

md5: b5ad3e2c5b42677f9f4191283388a8d7

Issue Description:

Hi Apple,

I've been re-syncing my swift repo and found I couldn't build a toolchain with beta 6 or beta 3 (as it suggests in the project README) giving an error building part of lldb saying _main undefined for architecture arm64. I've just successfully completed a build using beta 2 (the last beta before Apple Silicon). Should the README be updated or is there a specific reason why beta 3 is listed as the preferred version?

[LucianoPAlmeida]

@johnno1962 I had the same issue moving from beta 1 to beta 6, to build successfully you have to pass the --swift-darwin-supported-archs 'x86_64' flag on the build-script.
Perhaps this should have to be be in the docs somewhere

[johnno1962]

Thanks! I guess it should be.

[typesanitizer]

@swift-ci create