Merge pull request #13156 from AvaloniaUI/fix-build-baseline-version-parse

fix parsing the baseline version for api diff.

nukebuild/BuildParameters.cs

@@ -111,7 +111,7 @@ public partial class Build
             // VERSION
             Version = b.ForceNugetVersion ?? GetVersion();
 
-            ApiValidationBaseline = b.ApiValidationBaseline ?? new Version(new Version(Version).Major, 0).ToString();
+            ApiValidationBaseline = b.ApiValidationBaseline ?? new Version(new Version(Version.Split('-', StringSplitOptions.None).First()).Major, 0).ToString();
             UpdateApiValidationSuppression = b.UpdateApiValidationSuppression ?? IsLocalBuild;
             
             if (IsRunningOnAzure)