Add Mac Catalyst (iOS API, Mac ABI) runtime

[directhex]

This ties into several concurrent discussions:

#47645
#47517
#47518
#44882
dotnet/designs#174
#47768
dotnet/xamarin#29

I've made a few assumptions for now:

• RIDs will be maccatalyst-x64 and maccatalyst-arm64
• TFM is net6.0-maccatalyst
• TargetsMacCatalyst gets defined in the build
• IsMacCatalyst() and IsMacCatalystVersionAtLeast() get added to System.Runtime (an API change in need of review)
• --os maccatalyst gets passed to build.sh
• xharness support for maccatalyst Add Support for Mac Catalyst  xharness#435

It should work well enough right now to happily build a maccatalyst-x64 runtime pack. maccatalyst-arm64 requires an LLVM build, which we don't have as of today, plus a newer macOS/Xcode than my current dev machine. I know I've made some incorrect assumptions regarding ARM64 (e.g. the target iOS version for Catalyst needs to map to macOS 11.0+, but the number I'm using maps to 10.15.1)

[dotnet-issue-labeler]

Note regarding the new-api-needs-documentation label:

This serves as a reminder for when your PR is modifying a ref *.cs file and adding/modifying public APIs, to please make sure the API implementation in the src *.cs file is documented with triple slash comments, so the PR reviewers can sign off that change.

[ghost]

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Issue Details

---

This ties into several concurrent discussions:

#47645
#47517
#47518
#44882
dotnet/designs#174
#47768
dotnet/xamarin#29

I've made a few assumptions for now:

• RIDs will be maccatalyst-x64 and maccatalyst-arm64
• TFM is net6.0-maccatalyst
• TargetsMacCatalyst gets defined in the build
• IsMacCatalyst() and IsMacCatalystVersionAtLeast() get added to System.Runtime (an API change in need of review)
• --os maccatalyst gets passed to build.sh
• xharness ios will work with Catalyst apps, through addition of a maccatalyst test target (TODO)

It should work well enough right now to happily build a maccatalyst-x64 runtime pack. maccatalyst-arm64 requires an LLVM build, which we don't have as of today, plus a newer macOS/Xcode than my current dev machine. I know I've made some incorrect assumptions regarding ARM64 (e.g. the target iOS version for Catalyst needs to map to macOS 11.0+, but the number I'm using maps to 10.15.1)

Author:	directhex
Assignees:	-
Labels:	area-Infrastructure-libraries, new-api-needs-documentation
Milestone:	-

[directhex]

I haven't added yml to build the new stuff yet

[directhex]

Doesn't build with updated cmake. How exciting!

[directhex]

Relevant CMake issue is https://gitlab.kitware.com/cmake/cmake/-/issues/20132. I have a workaround, pushing to branch

[directhex]

ARM64 builds blocked on:

  /Users/directhex/Projects/runtime/src/mono/mono/mini/exceptions-arm64.c:552:2: warning: incompatible pointer to integer conversion assigning to '__uint64_t' (aka 'unsigned long long') from 'gpointer' (aka 'void *') [-Wint-conversion]
          UCONTEXT_REG_SET_PC (sigctx, addr);
          ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
  /Users/directhex/Projects/runtime/src/mono/mono/mini/../../mono/utils/mono-sigcontext.h:498:24: note: expanded from macro 'UCONTEXT_REG_SET_PC'
          UCONTEXT_REG_PC (ctx) = (val); \
                                ^ ~~~~~
  1 warning generated.

[directhex]

CI is boned today, and it's not my fault

[directhex]

ARM64 will be turned on when #47891 is fixed and merged

[directhex]

AppleAppBuilder needs serious work for Mac Catalyst ARM64, but should be good on x64

[directhex]

I've dispatched an official build, since my "oops it broke official builds" success rate isn't great

[directhex]

passed on internal