Use latest toolset, optionally use v141

[asklar]

allow building with v141, but use the latest toolset installed (v142 for VS2019) by default.

[JunielKatarn]

The only concern I have is the following:
Isn't v141 a requirement for dependent projects (i.e. Stellar)?

@acoates-ms do you know the current Universal toolset requirements for office?

[acoates-ms]

Yes Stellar needs v141, but the issue here is to allow both. Normal devs should use v142/VS2019 by default. But the nuget for stellar should use v141

[JunielKatarn]

This should be simple enough for developer workflows, especially if the VS solutions are now split.
We should discuss however how to approach the PR/CI automated builds.

• Should everything regarding universal be built only using v142?
• Should we add another strategy/matrix variant for v141|v142 toolsets?
• Should we only build v141 for those dependencies during the Publish pipeline?

[asklar]

The only concern I have is the following:
Isn't v141 a requirement for dependent projects (i.e. Stellar)?

@acoates-ms do you know the current Universal toolset requirements for office?

@KAnder425 was going to investigate if/why Stellar requires v141. Any updates on this?
=> last we heard, there is a crash that results when mixing 141 and 142 in the host app, but this hasn't been root caused. We should talk again about why stellar needs to stay on 141. This is making life complicated for everyone.

[chrisglein]

@KAnder425 Any updates on Stellar's v141 requirement?

[qmatteoq]

I add to this issue that moving to 142 would simplify a lot the adoption of Azure DevOps for building React Native for Windows projects. Currently you can't use a Hosted-Agent, but you're forced to use a private custom agent. The "vs2017-win2016" agent (which comes with Visual Studio 2017 and the v141 tools) isn't suitable because the project uses some C# 7.1 features, which are supported only by Visual Studio 2019. On the other side, the "windows-latest" image can't be leverage because the v141 platform toolset isn't installed in the Visual Studio 2019 version that comes with the hosted agent.