fix .NET 4.8.1 detection (#2067)

Author: adamsitnik

src/BenchmarkDotNet/Helpers/FrameworkVersionHelper.cs

@@ -11,6 +11,7 @@ internal static class FrameworkVersionHelper
         // should be ordered by release number
         private static readonly (int minReleaseNumber, string version)[] FrameworkVersions =
         {
+            (533320, "4.8.1"), // value taken from Windows 11 arm64 insider build
             (528040, "4.8"),
             (461808, "4.7.2"),
             (461308, "4.7.1"),
@@ -48,7 +49,7 @@ internal static string MapToReleaseVersion(string servicingVersion)
                 return "4.7.1";
             if (string.Compare(servicingVersion, "4.8") < 0)
                 return "4.7.2";
-            if (string.Compare(servicingVersion, "4.8.1") < 0)
+            if (string.Compare(servicingVersion, "4.8.9") < 0)
                 return "4.8";
 
             return "4.8.1"; // most probably the last major release of Full .NET Framework

tests/BenchmarkDotNet.Tests/FrameworkVersionHelperTests.cs

@@ -19,6 +19,9 @@ public class FrameworkVersionHelperTests
         [InlineData("4.7.3324.0", "4.7.2")]
         [InlineData("4.8", "4.8")]
         [InlineData("4.8.024", "4.8")]
+        [InlineData("4.8.4510.0", "4.8")]
+        [InlineData("4.8.4526.0", "4.8")]
+        [InlineData("4.8.9032.0", "4.8.1")]
         public void ServicingVersionsAreMappedToCorrespondingReleaseVersions(string servicingVersion, string expectedReleaseVersion)
         {
             Assert.Equal(expectedReleaseVersion, FrameworkVersionHelper.MapToReleaseVersion(servicingVersion));