housekeeping: Update to MSBuild.Sdk.Extras v2.0.24 and output API differences on DevOps builds.

[glennawatson]

Update to the latest.

[olevett]

👍

[glennawatson]

I made some changes to get this to work in the .net core 3 preview branch, will bring those across.

[codecov]

Codecov Report

Merging #2012 into master will decrease coverage by 0.1%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master    #2012      +/-   ##
==========================================
- Coverage   61.02%   60.92%   -0.11%     
==========================================
  Files         113      113              
  Lines        4565     4565              
  Branches      655      655              
==========================================
- Hits         2786     2781       -5     
- Misses       1598     1604       +6     
+ Partials      181      180       -1

Impacted Files	Coverage Δ
src/ReactiveUI.Winforms/RoutedViewHost.cs	87.5% <0%> (-2.78%)	⬇️
src/ReactiveUI.Winforms/ViewModelViewHost.cs	89.32% <0%> (-1.95%)	⬇️
src/ReactiveUI/RxApp.cs	81.33% <0%> (-1.34%)	⬇️

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