The command
   ./pre-inst-env guix-build hello
fails with

error: build failed: substituter `/usr/local/guix-
git/libexec/nix/substituters/download-using-manifests.pl' failed: error: 
executing `/usr/local/guix-git/libexec/nix/substituters/download-using-
manifests.pl': No such file or directory

We have by
find /usr/local/guix-git/libexec

/usr/local/guix-git/libexec
/usr/local/guix-git/libexec/guix
/usr/local/guix-git/libexec/guix/list-runtime-roots

Andreas