Add support for Alpine 3.13

[rbhanda]

This issue is created to track progress for the work to enable Alpine 3.13 support for .NET Core 2.1, 3.1 and .NET 5.

Product and Test updates

• [All teams] Do a compatibility check for the product with the new OS
• [CoreCLR/CoreFX] Runtime / RID Support update
• [Infra] Ensure that the correct Docker images used by teams are built in the dotnet-buildtools-prereqs (if applicable)
• [Infra] Replace docker tags used in builds across repos and branches
• [CLI team] Update CI legs to latest updated Dockerfile
• [All teams] Update test infrastructure to support the new version
• [Acquisition] Add support within nightly repos
• [Acquisition] Deploy to master (GA) during next patch release cycle

Release team:

• Notify .NET Core teams regarding new OS release
• Add feed for new OS release to packages.microsoft.com (if applicable)
• Update release manifest files
• Create new Docker files to test the new OS
• Update the supported OS content on GitHub and marketing sites.

Document updates:

• Add OS prerequisites to the dependencies document
• Update distro install page

---

Current Status:

Version	Available Date
.NET 5.0.3	9th Feb 20201
.NET Core 3.1.13	9th March 2021
.NET Core 2.1.26	9th March 2021

[adegeo]

@rbhanda should I update the docs install page now?

[rbhanda]

Hi @adegeo , yes. Please go ahead and update our install page for Alpine 3.13