To build the Source SDK 2013 on Linux you will need the Steam runtime. Install it using these instructions:
Download it here
tar xvf steam-runtime-sdk_latest.tar.xz
cd steam-runtime-sdk_<version> (replacing <version> with the version you just unpacked.)
./setup.sh (Pick your architecture and debug/release preferences and then answer Y to everything else.)
Then run "make -f game_<gamename>_linux32.mak". At this point you should have client.so and server.so files to load with the Source SDK Base 2013 of your choice. More instructions on using the Steam runtime can be found in README.txt in the installed runtime directory.