Fix build with Boost 1.89

Index: src/third_party/SConscript
--- src/third_party/SConscript.orig
+++ src/third_party/SConscript
@@ -345,7 +345,6 @@ if use_system_version_of_library("boost"):
             SYSLIBDEPS=[
                 env['LIBDEPS_BOOST_PROGRAM_OPTIONS_SYSLIBDEP'],
                 env['LIBDEPS_BOOST_FILESYSTEM_SYSLIBDEP'],
-                env['LIBDEPS_BOOST_SYSTEM_SYSLIBDEP'],
                 env['LIBDEPS_BOOST_IOSTREAMS_SYSLIBDEP'],
                 env['LIBDEPS_BOOST_THREAD_SYSLIBDEP'],
                 env['LIBDEPS_BOOST_LOG_SYSLIBDEP'],
@@ -359,7 +358,6 @@ else:
         LIBDEPS_INTERFACE=[
             boostDirectory + '/boost_program_options',
             boostDirectory + '/boost_filesystem',
-            boostDirectory + '/boost_system',
             boostDirectory + '/boost_iostreams',
             boostDirectory + '/boost_log',
         ])
