Solution for "SteamInternal_ContextInit" (pterodactyl#802)

Add required package to apt install

Solution for: error=/home/container/garrysmod/bin/server_srv.so: undefined symbol: SteamInternal_ContextInit

Author: Franco Sanllehi

database/seeds/eggs/source-engine/egg-garrys-mod.json

@@ -17,7 +17,7 @@
     },
     "scripts": {
         "installation": {
-            "script": "#!\/bin\/bash\n# Garry's Mod Installation Script\n#\n# Server Files: \/mnt\/server\napt -y update\napt -y --no-install-recommends install curl lib32gcc1 ca-certificates\n\ncd \/tmp\ncurl -sSL -o steamcmd.tar.gz http:\/\/media.steampowered.com\/installer\/steamcmd_linux.tar.gz\n\nmkdir -p \/mnt\/server\/steamcmd\ntar -xzvf steamcmd.tar.gz -C \/mnt\/server\/steamcmd\ncd \/mnt\/server\/steamcmd\n\n# SteamCMD fails otherwise for some reason, even running as root.\n# This is changed at the end of the install process anyways.\nchown -R root:root \/mnt\n\nexport HOME=\/mnt\/server\n.\/steamcmd.sh +login anonymous +force_install_dir \/mnt\/server +app_update 4020 +quit\n\nmkdir -p \/mnt\/server\/.steam\/sdk32\ncp -v linux32\/steamclient.so ..\/.steam\/sdk32\/steamclient.so",
+            "script": "#!\/bin\/bash\n# Garry's Mod Installation Script\n#\n# Server Files: \/mnt\/server\napt -y update\napt -y --no-install-recommends install curl lib32gcc1 lib32stdc++6 ca-certificates\n\ncd \/tmp\ncurl -sSL -o steamcmd.tar.gz http:\/\/media.steampowered.com\/installer\/steamcmd_linux.tar.gz\n\nmkdir -p \/mnt\/server\/steamcmd\ntar -xzvf steamcmd.tar.gz -C \/mnt\/server\/steamcmd\ncd \/mnt\/server\/steamcmd\n\n# SteamCMD fails otherwise for some reason, even running as root.\n# This is changed at the end of the install process anyways.\nchown -R root:root \/mnt\n\nexport HOME=\/mnt\/server\n.\/steamcmd.sh +login anonymous +force_install_dir \/mnt\/server +app_update 4020 +quit\n\nmkdir -p \/mnt\/server\/.steam\/sdk32\ncp -v linux32\/steamclient.so ..\/.steam\/sdk32\/steamclient.so",
             "container": "ubuntu:16.04",
             "entrypoint": "bash"
         }
@@ -42,4 +42,4 @@
             "rules": "required|string|alpha_num|size:32"
         }
     ]
-}
+}