fails to build against boost-1.89: missing boost_system

[ExecutorElassus]

As per this commit, boost has removed the boost_system library, which seems to be a dependency for electricsheep. On my (gentoo Linux) system, compilation fails with:

libtool: link: x86_64-pc-linux-gnu-g++ -DLINUX_GNU=1 -DSHAREDIR=\"/usr/share/electricsheep/\" -I/usr/include/libgtop-2.0 -I/usr/include/glib-2.0 -I/usr/lib64/glib-2.0/include -I/usr/include/lua5.1 -I/usr/include/libpng16 -I/usr/include/lua5.1 -D__STDC_CONSTANT_MACROS -Wno-write-strings -march=native -O2 -pipe -Wl,-O1 -Wl,-z -Wl,pack-relative-relocs -o electricsheep Player.o main.o Voting.o Hud.o Upload.o Download.o Networking.o LoadDDS.o Image.o RendererGL.o glx.o ShaderGL.o TextureFlatGL.o wgl.o FontGL.o mgl.o Shader.o Texture.o Font.o TextureFlat.o Renderer.o LoadPNG.o DisplayOutput.o tinyxmlparser.o tinyxml.o tinystr.o tinyxmlerror.o diriterator.o storage.o luastorage.o ContentDecoder.o SheepUploader.o ContentDownloader.o SheepGenerator.o SheepDownloader.o Sheep.o Shepherd.o LuaState.o Common.o AlignedBuffer.o isaac.o pool.o Log.o Rect.o luaxml.o Exception.o md5.o  -lz -Wl,--as-needed -lpthread -lboost_system -lavcodec -lavformat -lswscale -lavutil -llua5.1 -lGLEW -lGLU -lOpenGL -lcurl -lpng16 -lgtop-2.0 -lglib-2.0 -lXrender -lX11 -lrt -lGL -lglut -ltinyxml -lboost_filesystem -lboost_thread
/usr/lib/gcc/x86_64-pc-linux-gnu/15/../../../../x86_64-pc-linux-gnu/bin/ld: cannot find -lboost_system: No such file or directory
collect2: error: ld returned 1 exit status
make[1]: *** [Makefile:564: electricsheep] Error 1
make[1]: Leaving directory '/var/tmp/portage/app-misc/electricsheep-9999-r13/work/electricsheep-9999/client_generic/Client'
make: *** [Makefile:521: all-recursive] Error 1

Cheers