C#: Introduce delegate type in autobuilder

csharp/autobuilder/Semmle.Autobuild.Shared/Autobuilder.cs

@@ -19,6 +19,12 @@ namespace Semmle.Autobuild.Shared
         BuildScript Analyse(Autobuilder builder, bool auto);
     }
 
+    /// <summary>
+    /// A delegate used to wrap a build script in an environment where an appropriate
+    /// version of .NET Core is automatically installed.
+    /// </summary>
+    public delegate BuildScript WithDotNet(Autobuilder builder, Func<IDictionary<string, string>?, BuildScript> f);
+
     /// <summary>
     /// Exception indicating that environment variables are missing or invalid.
     /// </summary>

csharp/autobuilder/Semmle.Autobuild.Shared/BuildCommandAutoRule.cs

@@ -11,9 +11,9 @@ namespace Semmle.Autobuild.Shared
     /// </summary>
     public class BuildCommandAutoRule : IBuildRule
     {
-        private readonly Func<Autobuilder, Func<IDictionary<string, string>?, BuildScript>, BuildScript> withDotNet;
+        private readonly WithDotNet withDotNet;
 
-        public BuildCommandAutoRule(Func<Autobuilder, Func<IDictionary<string, string>?, BuildScript>, BuildScript> withDotNet)
+        public BuildCommandAutoRule(WithDotNet withDotNet)
         {
             this.withDotNet = withDotNet;
         }

csharp/autobuilder/Semmle.Autobuild.Shared/BuildCommandRule.cs

@@ -8,9 +8,9 @@ namespace Semmle.Autobuild.Shared
     /// </summary>
     public class BuildCommandRule : IBuildRule
     {
-        private readonly Func<Autobuilder, Func<IDictionary<string, string>?, BuildScript>, BuildScript> withDotNet;
+        private readonly WithDotNet withDotNet;
 
-        public BuildCommandRule(Func<Autobuilder, Func<IDictionary<string, string>?, BuildScript>, BuildScript> withDotNet)
+        public BuildCommandRule(WithDotNet withDotNet)
         {
             this.withDotNet = withDotNet;
         }