Then, from that build tree, type ‘source environment-variables’ (which
will setup the env. vars as they were during the build process), and
then ‘./check-guile ftw.test’.

This will print a line on stdout starting with “;;;”.  Please post that line.

What kernel are you using?  What file systems are involved?

Note that using pre-built binaries would allow to get past thing point,
because everything built fine on hydra.nixos.org.  But it’s a good idea
to investigate the failure, which may have something to do with the
Linux version or file system setup being used.

Thanks in advance,
Ludo’.