cherry-picked from
https://github.com/wesnoth/wesnoth/commit/b28c566d38c13352c4d97b4f804b23d491df038a

--- wesnoth-1.18.5/CMakeLists.txt
+++ wesnoth-1.18.5/CMakeLists.txt
@@ -93,7 +93,7 @@
 	find_library(SECURITY_LIBRARY Security REQUIRED)
 endif()
 
-find_package(Boost ${BOOST_VERSION} REQUIRED COMPONENTS iostreams program_options regex system thread random coroutine locale filesystem graph)
+find_package(Boost ${BOOST_VERSION} REQUIRED COMPONENTS iostreams program_options regex thread random coroutine locale filesystem graph)
 find_package(ICU REQUIRED COMPONENTS data i18n uc)
 
 # no, gettext executables are not required when NLS is deactivated
--- wesnoth-1.18.5/src/CMakeLists.txt
+++ wesnoth-1.18.5/src/CMakeLists.txt
@@ -248,7 +248,6 @@
 		Boost::iostreams
 		Boost::program_options
 		Boost::regex
-		Boost::system
 		Boost::random
 		Boost::coroutine
 		Boost::locale