workaround. fixed upstream:
https://github.com/arvidn/libtorrent/commit/680eddf3d421f97ba01e8c162b263f31693ba352

--- ./configure.orig
+++ ./configure
@@ -20267,7 +20267,6 @@
 
 COMPILETIME_OPTIONS="$COMPILETIME_OPTIONS -DBOOST_ASIO_HASH_MAP_BUCKETS=1021 "
 
-COMPILETIME_OPTIONS="$COMPILETIME_OPTIONS -msse4.2 "
 
 
 $as_echo "#define BOOST_EXCEPTION_DISABLE 1" >>confdefs.h
