Fix targetNet40 check in CompileVB

Author: siegfriedpammer

ICSharpCode.Decompiler.Tests/Helpers/Tester.VB.cs

@@ -46,7 +46,7 @@ public static async Task<CompilerResults> CompileVB(string sourceFileName, Compi
 				CompilerResults results = new CompilerResults();
 				results.PathToAssembly = outputFileName;
 
-				bool targetNet40 = (flags & CompilerOptions.TargetNet40) == 0;
+				bool targetNet40 = (flags & CompilerOptions.TargetNet40) != 0;
 
 				var (roslynVersion, languageVersion, targetFramework) = (flags & CompilerOptions.UseRoslynMask) switch {
 					0 => ("legacy", "11", null),