On Linux, with STEAM_RUNTIME=1 I still get libawesomium-1-7.so.0: cannot open shared object file

I just bought and installed the game on Steam Linux using Sabayon Linux 64 bits. All up to date, including the steam client.

Whenever I try to run the game it will just crash. So I went on and tried the suggestions in the Linux configuration thread and I run it from console.

csaba@csaba /media/medium/Csaba_Home_Extra/.local.share.Steam/ubuntu12_32/steam-runtime $ ./run.sh ../../SteamApps/common/Natural\ Selection\ 2/ns2_linux32 
GetInstanceCount currently unimplemented
Build 254
Linux
/media/medium/Csaba_Home_Extra/.local.share.Steam/SteamApps/common/Natural Selection 2/system/awesomium/awesomium_process: error while loading shared libraries: libawesomium-1-7.so.0: cannot open shared object file: No such file or directory
Setting breakpad minidump AppID = 4920
Steam_SetMinidumpSteamID:  Caching Steam ID:  76561198082125608 [API loaded no]
Steam initialized
Error: Attempted to load remote options from a file that does not exist.
Error: Loading of cloud user settings failed
Segmentation fault

Of course, Steam client is started with runtime=1.

csaba@csaba ~ $ STEAM_RUNTIME=1 steam

I could find no solution to this problem, nor the missing library.

Thank you for your support.