test(ci): .NET 5.0 with MSBuild 16

[jpnurmi]

This PR adds an integration test that builds and runs a minimal Sentry .NET app with different .NET SDK and MSBuild versions:

• .NET 5.0 (MSBuild 16, excluded on macOS)
• .NET 8.0 (MSBuild 17)
• .NET 9.0 (MSBuild 17)

.NET 5.0 installation and tests are excluded on macOS because .NET 5.0 does not support ARM64 on macOS. However, the test reproduces the warning reported in #4554 both on Windows and Linux:

Once #4554 has been fixed, we could consider TreatWarningsAsErrors=true to prevent new warnings from surfacing in the future.

Close: #4299

#skip-changelog

---

Note

Adds MSBuild integration tests for .NET 5/8/9 and updates CI to install .NET 5 SDK and libssl1 on Linux, plus packs during MSBuild.

• CI
  • Install legacy libssl1.1 on Linux via scripts/install-libssl1.sh in ./github/actions/environment.
  • Install .NET 5.0 SDK (excluded on macOS ARM64) alongside existing SDK setup.
  • MSBuild job now runs Restore,Build,Pack and executes integration tests via integration-test/msbuild.Tests.ps1.
• Integration Tests
  • New integration-test/msbuild.Tests.ps1 builds/runs a console app via MSBuild across net5.0 (when supported), net8.0, and net9.0, validating Sentry capture.
  • Add integration-test/nuget5.config for NuGet 5 (no packageSourceMapping) used with .NET 5.
  • Update integration-test/common.ps1 to use dotnet restore /p:CheckEolTargetFramework=false.
• Scripts
  • Add scripts/install-libssl1.sh to install openssl1.1-compat (Alpine) or libssl1.1 (Ubuntu).

^{Written by Cursor Bugbot for commit dc2ddfd. This will update automatically on new commits. Configure here.}

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 73.47%. Comparing base (fc55d48) to head (dc2ddfd).
⚠️ Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #4569      +/-   ##
==========================================
+ Coverage   73.46%   73.47%   +0.01%     
==========================================
  Files         482      482              
  Lines       17679    17679              
  Branches     3495     3495              
==========================================
+ Hits        12988    12990       +2     
+ Misses       3800     3798       -2     
  Partials      891      891              

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[jpnurmi]

@Flash0ver Turns out we didn't need microsoft/setup-msbuild nor choco install visualstudio2019buildtools for this.

On the contrary, injecting MSBuild 16 into PATH would break the dotnet (9) command that we need to be able to execute for some preparational steps in the integration tests with global.json in the project root.

Fortunately, the same warning can be produced with dotnet msbuild with .NET 5.0 and MSBuild 16 installed on the side.

[Flash0ver]

This is Amazing.MaxValue! It will give us more coverage and confidence when making changes to non-/lib/ Assets, like /build/(*.props|.targets) and /analyzers/* (Compiler Extensions like Source Generators) 🥔

[Flash0ver]

Well done!

• no more NETSDK1138 on .NET 5 reported
• but CS8032 reported on .NET 5 SDK, indeed utilizing MSBuild 16.11

Got one final (non-blocking) nitpick related to another PR currently in review: