A variant of this launcher ships in every game I've worked on. While the filename here is GameName.sh, I do not use the .sh extension. Just `chmod +x` this and put your OSX bins in osx/, Linux 32-bit bins in x86/, and Linux 64-bit bins in x86_64/.

GameName.sh

#!/bin/bash
# GameName Shell Script
# Written by Ethan "flibitijibibo" Lee

# Move to script's directory
cd "`dirname "$0"`"

# Get the kernel/architecture information
UNAME=`uname`
ARCH=`uname -m`

# Set the libpath and pick the proper binary
if [ "$UNAME" == "Darwin" ]; then
    export DYLD_LIBRARY_PATH=$DYLD_LIBRARY_PATH:./osx/
    ./osx/gamename.osx
elif [ "$UNAME" == "Linux" ]; then
    if [ "$ARCH" == "x86_64" ]; then
        export LD_LIBRARY_PATH=$LD_LIBRARY_PATH:./x86_64/
        ./x86_64/gamename.x86_64
    else
        export LD_LIBRARY_PATH=$LD_LIBRARY_PATH:./x86/
        ./x86/gamename.x86
    fi
fi

Wouldn't this technique result in an intermediate shell process hanging around until the program exits? Something like:

bash
`- GameName.sh
    `- gamename.x86_64

Are signals handled correctly? Would it be better to use exec ./x86_64/gamename.x86_64 to replace the running shell process?