[Android] Enable building CoreCLR for Android

[kotlarmilos]

Improve build infrastructure

• Resolve TCP/IP EventPipe support on CoreCLR Android #111524
• Export System.Security.Cryptography APIs for singlefilehost in CoreCLR build for Android #111523
• Fix libunwind errors in CoreCLR Android build #111527
• Set ANDROID_PLATFORM internally in the build
• Remove duplicate defines for CORECLR_HOSTING_API_LINKAGE
• Clean up CoreCLR cross build issues: During cross build, the same obj directory is used for target and host libunwind compilation #111868
• Consider static linking and componentization of CoreCLR runtime #114737
• [Mobile] Implement CMake export module for CoreCLR on Android and Apple mobile #115362

Build support

• [android] Update internal documentation on CoreCLR on Android experimental support #112034
• Beginnings of native Android build #110471
• Bring up android+coreclr windows build.  #112256
• Support builds for arm, x86 architectures
  • [Android] fseeko and ftello not supported on arm32 & x86 below API level 24 without disabling _FILE_OFFSET_BITS=64 #111665
• Support cross-building on Windows
  • Add Microsoft.NETCore.App.Crossgen2.android-<arch> packs with the hosting R2R target for Android

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[steveisok]

@kotlarmilos I added an item to track building Android on Windows. Current state is not going to work.

[akoeplinger]

I have some changes on a branch somewhere that make building Android on Windows (using mono) almost work, I can upstream those.