Enable ASP.NET Core on Apple Silicon

[sdmaclea]

Apple has announced plans to transition its Mac hardware line to a new Arm64-based chip that they refer to as “Apple Silicon

See dotnet/runtime#43313

This issue tracks work to enable ASP.NET Core on Apple Silicon

• Enable compilation on Apple Silicon
• Enable cross compilation from osx-x64
• Add arm64 support to SQLitePCL.raw osx universal binary Support Apple Silicon for e_sqlite3 ericsink/SQLitePCL.raw#375
• Add arm64 support to libuv osx universal binary (optional?) Libuv removed.
• Enable CI builds
• Enable testing

The first three items have been completed for the dotnet/runtime and should be able to proceed for aspnetcore.

Hints from dotnet/runtime learnings:

• Cross compilation requires Xcode 12.2 or better (included in vmImage 10.15)
• pass -arch arm64 to the clang compiler to select arm64 as the target architecture.

[sdmaclea]

Depends on a newer .NET 6 runtime. The current version is 4 days old. See #26693. Runtime 6.0.0-alpha.1.20509.10 seems to have a osx-arm64.

[sdmaclea]

Waiting on #26788