Set useCuda if CUDA enabled in Compression class.

src/nvtt/CompressionOptions.h

@@ -46,7 +46,7 @@ namespace nvtt
 		uint bmask;
 		uint amask;
 		
-		bool useCuda;
+		mutable bool useCuda;
 
 		nv::String externalCompressor;
 

src/nvtt/nvtt.cpp

@@ -673,6 +673,9 @@ static bool compress(const InputOptions::Private & inputOptions, const OutputOpt
 /// Compress the input texture with the given compression options.
 bool Compressor::process(const InputOptions & inputOptions, const CompressionOptions & compressionOptions, const OutputOptions & outputOptions) const
 {
+	// @@ Hack!
+	compressionOptions.m.useCuda = this->m.cudaEnabled;
+
 	return ::compress(inputOptions.m, outputOptions.m, compressionOptions.m);
 }