Detect .net core backing dll

src/Squirrel/SquirrelAwareExecutableDetector.cs

@@ -28,9 +28,27 @@ namespace Squirrel
         {
             if (!File.Exists(executable)) return null;
             var fullname = Path.GetFullPath(executable);
+            var backingDll = fullname.Substring(0, fullname.Length - 3) + "dll";
+            
+            return Utility.Retry<int?>(() =>
+            {
+                var assemblySquirrelAwareVersion = GetAssemblySquirrelAwareVersion(fullname);
+                if (assemblySquirrelAwareVersion != null)
+                {
+                    return assemblySquirrelAwareVersion;
+                }
 
-            return Utility.Retry<int?>(() => 
-                GetAssemblySquirrelAwareVersion(fullname) ?? GetVersionBlockSquirrelAwareValue(fullname));
+                if (File.Exists(backingDll))
+                {
+                    var assemblyDllSquirrelAwareVersion = GetAssemblySquirrelAwareVersion(backingDll);
+                    if (assemblyDllSquirrelAwareVersion != null)
+                    {
+                        return assemblyDllSquirrelAwareVersion;
+                    }
+                }
+
+                return GetVersionBlockSquirrelAwareValue(fullname);
+            });
         }
 
         static int? GetAssemblySquirrelAwareVersion(string executable)

test/SquirrelAwareExecutableDetectorTests.cs

@@ -44,13 +44,22 @@ namespace Squirrel.Tests
         [Fact]
         public void SquirrelAwareViaLanguageNeutralVersionBlock()
         {
-            var target = IntegrationTestHelper.GetPath("fixtures", "SquirrelAwareNetCoreApp.exe");
+            var target = IntegrationTestHelper.GetPath("fixtures", "SquirrelAwareTweakedNetCoreApp.exe");
             Assert.True(File.Exists(target));
 
             var ret = SquirrelAwareExecutableDetector.GetPESquirrelAwareVersion(target);
             Assert.Equal(1, ret.Value);
         }
 
+        [Fact]
+        public void SquirrelAwareViaNetCoreAssemblyAttribute()
+        {
+            var target = IntegrationTestHelper.GetPath("fixtures", "SquirrelAwareNetCoreApp.exe");
+            Assert.True(File.Exists(target));
+
+            var ret = SquirrelAwareExecutableDetector.GetPESquirrelAwareVersion(target);
+            Assert.Equal(1, ret.Value);
+        }
 
         [Fact]
         public void SquirrelAwareViaAssemblyAttribute()