Fix designer errors and .NET Framework on Unix errors.

src/Avalonia.DesktopRuntime/Avalonia.DesktopRuntime.csproj

@@ -16,5 +16,6 @@
   </ItemGroup>
 
   <Import Project="..\..\build\NetCore.props" />
+  <Import Project="..\..\build\NetFX.props" />
   <Import Project="..\Shared\PlatformSupport\PlatformSupport.projitems" />
 </Project>

src/tools/Avalonia.Designer.HostApp/Avalonia.Designer.HostApp.csproj

@@ -18,4 +18,6 @@
     <ProjectReference Include="..\..\Avalonia.Styling\Avalonia.Styling.csproj" />
     <ProjectReference Include="..\..\Avalonia.Themes.Default\Avalonia.Themes.Default.csproj" />
   </ItemGroup>
+
+  <Import Project="..\..\..\build\NetFX.props" />
 </Project>

src/tools/Avalonia.Designer.HostApp/Program.cs

@@ -2,20 +2,19 @@
 using System.IO;
 using System.Reflection;
 
-namespace Avalonia.Designer.HostApp.NetFX
+namespace Avalonia.Designer.HostApp
 {
     class Program
     {
-#if NET461
         private static string s_appDir;
         
         private static Assembly CurrentDomain_AssemblyResolve(object sender, ResolveEventArgs args)
         {
             string assemblyPath = Path.Combine(s_appDir, new AssemblyName(args.Name).Name + ".dll");
             if (File.Exists(assemblyPath) == false) return null;
-            Assembly assembly = Assembly.LoadFrom(assemblyPath);
-            return assembly;
+            return Assembly.LoadFile(assemblyPath);
         }
+
         public static void Main(string[] args)
         {
             s_appDir = Directory.GetCurrentDirectory();
@@ -36,9 +35,6 @@ namespace Avalonia.Designer.HostApp.NetFX
         }
 
         static void Exec(string[] args)
-#elif NETCOREAPP2_0
-        public static void Main(string[] args)
-#endif
         {
             Avalonia.DesignerSupport.Remote.RemoteDesignerEntryPoint.Main(args);
         }

tests/Avalonia.DesignerSupport.Tests/DesignerSupportTests.cs

@@ -101,6 +101,7 @@ namespace Avalonia.DesignerSupport.Tests
                     RedirectStandardOutput = true,
                     RedirectStandardError = true,
                     CreateNoWindow = true,
+                    WorkingDirectory = outputDir,
                 },
                 EnableRaisingEvents = true
             })
@@ -117,7 +118,7 @@ namespace Avalonia.DesignerSupport.Tests
                     cancelled = true;
                 }
 
-                Assert.True(cancelled);
+                Assert.True(cancelled, $"Message Not Received.");
                 Assert.NotEqual(0, handle);
                 proc.Kill();
                 proc.WaitForExit();