Bug: https://bugs.gentoo.org/963777

--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -105,7 +105,7 @@ SET (Boost_DEBUG FALSE)
 SET (Boost_USE_MULTITHREADED ${BOOST_MULTITHREADED_BUILD})
 SET (Boost_USE_STATIC_LIBS ${BOOST_STATIC_BUILD})
 
-FIND_PACKAGE(Boost COMPONENTS filesystem regex date_time thread system)
+FIND_PACKAGE(Boost COMPONENTS filesystem regex date_time thread OPTIONAL_COMPONENTS system)
 
 if(Boost_FOUND)
   INCLUDE_DIRECTORIES(${Boost_INCLUDE_DIRS})