Support targeting iOS platforms with ILCompiler

[ivanpovazan]

Description

ILCompiler does not support generating code for iOS platforms.

Proposal

Enable ILCompiler to support targeting the following set of platforms (target operating system and architecture combinations):

• ios-arm64
• iossimulator-arm64/x64

The implementation should include and is not limited to the following:

• Extend the supported set of target operating systems with identifiers for iOS platforms
• Enable the compiler to accept the newly added identifiers
• Adjust the source code to target iOS platforms similarly to targeting OSX
• Add the correct LLVM-triple resolution for iOS platforms

Tagging subscribers to this area: @agocke, @MichalStrehovsky, @jkotas
See info in area-owners.md if you want to be subscribed.

Issue Details

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Author:	ivanpovazan
Assignees:	-
Labels:	untriaged, area-NativeAOT-coreclr
Milestone:	-

Tagging subscribers to 'os-ios': @steveisok, @akoeplinger
See info in area-owners.md if you want to be subscribed.

Issue Details

---

null

Author:	ivanpovazan
Assignees:	-
Labels:	os-ios, area-NativeAOT-coreclr
Milestone:	-