Try to fix AppVeyor build.

ICSharpCode.Decompiler/Tests/RoundtripAssembly.cs

@@ -162,6 +162,9 @@ namespace ICSharpCode.Decompiler.Tests
 			info.CreateNoWindow = true;
 			info.UseShellExecute = false;
 			info.RedirectStandardOutput = true;
+			// Don't let environment variables (e.g. set by AppVeyor) influence the build.
+			info.EnvironmentVariables.Remove("Configuration");
+			info.EnvironmentVariables.Remove("Platform");
 			Console.WriteLine($"\"{info.FileName}\" {info.Arguments}");
 			using (var p = Process.Start(info)) {
 				Regex errorRegex = new Regex(@"^[\w\d.\\-]+\(\d+,\d+\):");

clean.bat

@@ -1,4 +1,4 @@
-@if not exist "AvalonEdit\ICSharpCode.AvalonEdit.sln" (
+@if not exist "NRefactory\NRefactory.sln" (
 	git submodule update --init || exit /b 1
 )
 %windir%\microsoft.net\framework\v4.0.30319\msbuild /m ILSpy.sln /t:clean "/p:Platform=Any CPU" /p:Configuration=Debug

debugbuild.bat

@@ -1,4 +1,4 @@
-@if not exist "AvalonEdit\ICSharpCode.AvalonEdit.sln" (
+@if not exist "NRefactory\NRefactory.sln" (
 	git submodule update --init || exit /b 1
 )
 "%ProgramFiles(x86)%\MSBuild\14.0\Bin\msbuild.exe" /m ILSpy.sln /p:Configuration=Debug "/p:Platform=Any CPU"

releasebuild.bat

@@ -1,4 +1,4 @@
-@if not exist "AvalonEdit\ICSharpCode.AvalonEdit.sln" (
+@if not exist "NRefactory\NRefactory.sln" (
 	git submodule update --init || exit /b 1
 )
 "%ProgramFiles(x86)%\MSBuild\14.0\Bin\msbuild.exe" /m ILSpy.sln /p:Configuration=Release "/p:Platform=Any CPU"