Avoid api validation for symbol packages

nukebuild/ApiDiffValidation.cs

@@ -38,7 +38,8 @@ public static class ApiDiffValidation
             var left = new List<string>();
             var right = new List<string>();
 
-            var suppressionFile = Path.Combine(suppressionFilesFolder, GetPackageId(packagePath) + ".nupkg.xml");
+            var packageId = GetPackageId(packagePath);
+            var suppressionFile = Path.Combine(suppressionFilesFolder, packageId + ".nupkg.xml");
 
             // Don't use Path.Combine with these left and right tool parameters.
             // Microsoft.DotNet.ApiCompat.Tool is stupid and treats '/' and '\' as different assemblies in suppression files.
@@ -57,7 +58,7 @@ public static class ApiDiffValidation
                     e.target == baselineDll.target && e.entry.Name == baselineDll.entry.Name);
                 if (targetDll.entry is null)
                 {
-                    throw new InvalidOperationException($"Some assemblies are missing in the new package: {baselineDll.entry.Name} for {baselineDll.target}");
+                    throw new InvalidOperationException($"Some assemblies are missing in the new package {packageId}: {baselineDll.entry.Name} for {baselineDll.target}");
                 }
 
                 var targetDllPath = $"target/{targetDll.target}/{targetDll.entry.Name}";

nukebuild/Build.cs

@@ -288,7 +288,7 @@ partial class Build : NukeBuild
         .Executes(async () =>
         {
             await Task.WhenAll(
-                Directory.GetFiles(Parameters.NugetRoot).Select(nugetPackage => ApiDiffValidation.ValidatePackage(
+                Directory.GetFiles(Parameters.NugetRoot, "*.nupkg").Select(nugetPackage => ApiDiffValidation.ValidatePackage(
                     ApiCompatTool, nugetPackage, Parameters.ApiValidationBaseline,
                     Parameters.ApiValidationSuppressionFiles, Parameters.UpdateApiValidationSuppression)));
         });