Fix mpu -l does not work in current source.

Author: yfakariya

src/mpu/AssetFileImporter.cs

@@ -94,17 +94,19 @@ public void AssembleAssetTree( string sourceProjectPath, string outputDirectoryP
 
 			var sourceDirectoryPath = Path.GetDirectoryName( sourceProjectPath );
 			var relativePrefix = ".." + Path.DirectorySeparatorChar;
-			foreach ( var sourceFileRelativePath in this.ParseProjectFile( sourceProjectPath ).Select( p => p.Replace( '\\', Path.DirectorySeparatorChar )) )
+			foreach ( var sourceFileRelativePath in this.ParseProjectFile( sourceProjectPath ).Select( p => p.Replace( '\\', Path.DirectorySeparatorChar ) ) )
 			{
 				var destinationFilePath = 
 					Path.Combine( 
 						outputDirectoryPath,
-						new String(
-							( sourceFileRelativePath.StartsWith( relativePrefix ) ? sourceFileRelativePath.Substring( 3 ) : sourceFileRelativePath ) // remove relative
+						sourceFileRelativePath.StartsWith( relativePrefix )
+						? new String(
+							sourceFileRelativePath.Substring( 3 ) // remove relative
 							.SkipWhile( c => c != Path.DirectorySeparatorChar) // remove project name portion
 							.Skip( 1 )
 							.ToArray()
 						)
+						: sourceFileRelativePath // descendant path only
 					);
 				// ReSharper disable once AssignNullToNotNullAttribute
 				Directory.CreateDirectory( Path.GetDirectoryName( destinationFilePath ) );