msg/async/compression_onwire: include used header

this fixes the FTBFS with Clang + libc++.

Signed-off-by: Kefu Chai <kchai@redhat.com>

diff --git a/src/msg/async/compression_onwire.h b/src/msg/async/compression_onwire.h
index e90274a6c5c4aad8cddcf1afe37154cd07431d9a..dcd6d26c4ca3097d37b087fdfa6f137630212adc 100644 (file)
--- a/src/msg/async/compression_onwire.h
+++ b/src/msg/async/compression_onwire.h
@@ -4,6 +4,8 @@
 #ifndef CEPH_COMPRESSION_ONWIRE_H
 #define CEPH_COMPRESSION_ONWIRE_H
 
+#include <optional>
+
 #include "compressor/Compressor.h"
 #include "include/buffer.h"