Fix build on older APIs that don't have <mutex>

GOLDFISH_VULKAN can be a proxy for that.

Change-Id: Idab98cce3f99d387da61985a3fb42e7fb51a5834
diff --git a/system/OpenglSystemCommon/HostConnection.h b/system/OpenglSystemCommon/HostConnection.h
index 098dadc..e46c3aa 100644
--- a/system/OpenglSystemCommon/HostConnection.h
+++ b/system/OpenglSystemCommon/HostConnection.h
@@ -24,7 +24,12 @@
 
 #include <cutils/native_handle.h>
 
+#ifdef GOLDFISH_VULKAN
 #include <mutex>
+#else
+#include <utils/threads.h>
+#endif
+
 #include <string>
 
 class GLEncoder;
@@ -167,7 +172,11 @@
     std::string m_glExtensions;
     bool m_grallocOnly;
     bool m_noHostError;
+#ifdef GOLDFISH_VULKAN
     mutable std::mutex m_lock;
+#else
+    mutable android::Mutex m_lock;
+#endif
 };
 
 #endif