Try fix some stuff

Author: andrewlock

tracer/build/_build/Build.Steps.cs

@@ -96,24 +96,9 @@ partial class Build
     [LazyPathExecutable(name: "otool")] readonly Lazy<Tool> OTool;
     [LazyPathExecutable(name: "lipo")] readonly Lazy<Tool> Lipo;
 
-    TargetPlatform[] ArchitecturesForPlatformForTracer
-        => (TargetPlatform, PlatformRequirement) switch
-    {
-        (_, PlatformRequirement.Single) => new[] { TargetPlatform },
-        (TargetPlatform.x64, PlatformRequirement.ForceWindowsArm64) => new[] { TargetPlatform.x64, TargetPlatform.x86, TargetPlatform.arm64ec },
-        (TargetPlatform.x64, PlatformRequirement.Default) => new[] { TargetPlatform.x64, TargetPlatform.x86 },
-        (TargetPlatform.arm64, _) => new[] { TargetPlatform.x64, TargetPlatform.x86, TargetPlatform.arm64ec },
-        (TargetPlatform.x86, _) => new[] { TargetPlatform.x86 },
-        _ => new[] { TargetPlatform },
-    };
+    TargetPlatform[] ArchitecturesForPlatformForTracer => Architectures(supportsWindowsArm64: true);
 
-    TargetPlatform[] ArchitecturesForPlatformForProfiler
-        => TargetPlatform switch
-        {
-            TargetPlatform.x64 => new[] { TargetPlatform.x64, TargetPlatform.x86 },
-            TargetPlatform.x86 => new[] { TargetPlatform.x86 },
-            _ => new[] { TargetPlatform },
-        };
+    TargetPlatform[] ArchitecturesForPlatformForProfiler => Architectures(supportsWindowsArm64: false);
 
     bool IsArm64 => RuntimeInformation.ProcessArchitecture == Architecture.Arm64;
     string UnixArchitectureIdentifier => IsArm64 ? "arm64" : TargetPlatform.ToString();
@@ -343,11 +328,8 @@ TargetPlatform[] ArchitecturesForPlatformForProfiler
         .OnlyWhenStatic(() => IsWin)
         .Executes(() =>
         {
-            // If we're building for x64, build for x86 too
-            var platforms =
-                Equals(TargetPlatform, MSBuildTargetPlatform.x64)
-                    ? new[] { MSBuildTargetPlatform.x64, MSBuildTargetPlatform.x86 }
-                    : new[] { MSBuildTargetPlatform.x86 };
+            // Tests don't support arm64 on Windows
+            var platforms = Architectures(supportsWindowsArm64: false);
 
             // Can't use dotnet msbuild, as needs to use the VS version of MSBuild
             MSBuild(s => s
@@ -2274,4 +2256,15 @@ private void DotnetBuild(
             .SetProcessArgumentConfigurator(arg => arg.Add("/nowarn:NU1701")) //nowarn:NU1701 - Package 'x' was restored using '.NETFramework,Version=v4.6.1' instead of the project target framework '.NETCoreApp,Version=v2.1'.
             .CombineWith(projPaths, (settings, projPath) => settings.SetProjectFile(projPath)));
     }
+
+    TargetPlatform[] Architectures(bool supportsWindowsArm64)
+    => (RuntimeInformation.IsOSPlatform(OSPlatform.Windows), TargetPlatform, PlatformRequirement, supportsArm64: supportsWindowsArm64) switch
+    {
+        (true, TargetPlatform.arm64 or TargetPlatform.arm64ec, PlatformRequirement.Single, false) => throw new Exception($"Requested {TargetPlatform} platform build on Windows, but ARM64 is not supported"),
+        (_, _, PlatformRequirement.Single, _) => new[] { TargetPlatform },
+        (true, TargetPlatform.x64, PlatformRequirement.ForceWindowsArm64, true) => new[] { TargetPlatform.x64, TargetPlatform.x86, TargetPlatform.arm64ec },
+        (_, TargetPlatform.x64, PlatformRequirement.ForceWindowsArm64 or PlatformRequirement.Default, _) => new[] { TargetPlatform.x64, TargetPlatform.x86},
+        (false, TargetPlatform.arm64, _, _) => new[] { TargetPlatform.x64, TargetPlatform.x86, TargetPlatform.arm64ec },
+        _ => new[] { TargetPlatform },
+    };
 }