lockable: workaround GCC link issue with ASAN

Current GCC has an optimization bug when compiling with ASAN.

See also GCC bug:
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=84307Signed-off-by: NMarc-André Lureau <marcandre.lureau@redhat.com>
Message-Id: <20180215212552.26997-3-marcandre.lureau@redhat.com>
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>

include/qemu/lockable.h

@@ -28,7 +28,7 @@ struct QemuLockable {
  * to QEMU_MAKE_LOCKABLE.  For optimized builds, we can rely on dead-code elimination
  * from the compiler, and give the errors already at link time.
  */
-#ifdef __OPTIMIZE__
+#if defined(__OPTIMIZE__) && !defined(__SANITIZE_ADDRESS__)
 void unknown_lock_type(void *);
 #else
 static inline void unknown_lock_type(void *unused)