cegma.rb: fix for installation on Linux

On my Linux system, CEGMA cannot be installed, make crashes with:

```  ArgumentError: different prefix: "" and "[..]/.linuxbrew/Cellar/cegma/2.4.010312/bin"```

This is the backtrace:

```
/gpfs/cyberstar/p/pzm11/nobackup/rxc48/.linuxbrew/Library/Homebrew/extend/pathname.rb:85:in `install_symlink_p'
/gpfs/cyberstar/p/pzm11/nobackup/rxc48/.linuxbrew/Library/Homebrew/extend/pathname.rb:77:in `install_symlink'
/gpfs/cyberstar/p/pzm11/nobackup/rxc48/.linuxbrew/Library/Homebrew/extend/pathname.rb:70:in `each'
/gpfs/cyberstar/p/pzm11/nobackup/rxc48/.linuxbrew/Library/Homebrew/extend/pathname.rb:70:in `install_symlink'
/gpfs/cyberstar/p/pzm11/nobackup/rxc48/.linuxbrew/Library/Formula/cegma.rb:20:in `install'
```

The attached patch does two things:
1) It fixes this error
2) It also copies all other binaries created by CEGMA (not just the ```cegma``` binary)