Emit mspack debug messages to Xenia.

third_party/mspack/logging.cc

@@ -0,0 +1,10 @@
+#include "xenia/base/logging.h"
+
+extern "C" void xenia_log(const char* fmt, ...) {
+  char buffer[128];
+  va_list args;
+  va_start(args, fmt);
+  vsnprintf(buffer, sizeof(buffer), fmt, args);
+  va_end(args);
+  XELOGW("mspack: %s", buffer);
+}