liblzma: Remove non-portable empty initializer.

Commit 78704f36e74205857c898a351c757719a6c8b666 added an empty
initializer {} to prevent a warning. The empty initializer is a GNU
extension and results in a build failure on MSVC. The -wpedantic flag
warns about empty initializers.

src/liblzma/common/stream_encoder_mt.c

@@ -743,7 +743,7 @@ stream_encode_mt(void *coder_ptr, const lzma_allocator *allocator,
 
 		// These are for wait_for_work().
 		bool has_blocked = false;
-		mythread_condtime wait_abs = {};
+		mythread_condtime wait_abs = { 0 };
 
 		while (true) {
 			mythread_sync(coder->mutex) {