Installing x64 gfortran binaries - problems with libisl.so

I am trying to install gfortran (needed to build Julia) on a fairly locked-down VM. Following the instructions here I checked out everything from gcc-trunk, added gcc-trunk / bin to the path and gfortran -version works. However, whenever I try to use it, I get an error along the lines

bash-3.00$ gfortran hello.f90
/path/to/gcc-trunk/bin/../libexec/gcc/x86_64-unknown-linux-gnu/6.0.0/f951: error while loading shared libraries: libisl.so.13: cannot open shared object file: No such file or directory
bash-3.00$ echo $LD_LIBRARY_PATH
/path/to/gcc-trunk/lib64

      

        
        
        
      

    

where / path / to is the actual (rather long path). libisl.so.13 was not in this directory, but it was included in the gcc-5 infrastructure file. I grabbed the libraries and added them to the lib64 folder. Now I am getting the following error:

bash-3.00$ gfortran hello.f90
/path/to/gcc-trunk/bin/../libexec/gcc/x86_64-unknown-linux-gnu/6.0.0/f951: error while loading shared libraries: /path/to/gcc-trunk/lib64/libisl.so.13: file too short

      

        
        
        
      

    

This file only contains the text "libisl.so.13.1.0", which is another 1.5 MB file in the same directory. Is there something else I need to make sure gfortran is pointing to the second file?