Fix relative pragma tests

When relative pragmas are enabled, and includes already have relative
path, and there is no base bath from which to calculate relative paths,
use the existing relative path as-is.

Mono.TextTemplating/Mono.TextTemplating/TemplatingEngine.CodeGeneration.cs

@@ -98,8 +98,10 @@ static void GenerateTransformMethod (CodeTypeDeclaration templateType, TemplateS
 				if (!settings.NoLinePragmas) {
 					var filename = seg.StartLocation.FileName ?? templateFile;
 					if (!string.IsNullOrEmpty (filename)) {
-						filename = Path.GetFullPath (filename);
-						if (pragmasRelativeToDirectory is not null) {
+						if (!settings.RelativeLinePragmas) {
+							filename = Path.GetFileName (filename);
+						} else if (pragmasRelativeToDirectory is not null) {
+							filename = Path.GetFullPath (filename);
 							filename = FileUtil.AbsoluteToRelativePath (pragmasRelativeToDirectory, filename);
 						}
 					}