> You would need to add a phase to do:

>   (patch-shebang "the/faulty/file")

> That would change /usr/bin/env to /nix/store/xxx/bin/env.

The problem is that I haven't found any references to '/usr/bin/env' in
those files. I tried the following anyway, but it didn't work out.

  (arguments '(#:phases
               (alist-cons-before
                'build 'patch-/usr/bin/env
                (lambda _
                  (for-each patch-shebang
                            '("gio/tests/gdbus-test-codegen-generated.c"
                              "gio/tests/gdbus-test-codegen-generated.h")))
                %standard-phases)))

Nikita