Guix 1.4 unable to pull with --no-substitutes

[tobtoht <tob@featherwallet.org>]

Hi,

Using guix 1.4.0 as a starting point on a foreign distro, I'm unable to
complete a pull without substitutes.

Steps to reproduce:

$ install guix using the installer script (or apt install guix)
$ export GUIX_BUILD_OPTIONS="--no-substitutes"
$ guix pull

It then proceeds to build a number of packages, including guile 3.0.7. Tests 
for this package fail as described here: https://issues.guix.gnu.org/48392

I have tried building it at least a dozen times and the tests fail each time.

Context:

A project I am involved with uses guix time-machine + guix shell to set up a
build environment that is used to build portable binaries for a desktop 
application. For security and auditability reasons, the build process is 
bootstrappable and verifiably reproducible.

Multiple builders build the software using guix. The results are signed, 
submitted to a central repository, and compared.

To ensure the build is in fact bootstrappable, and to detect potential 
non-determinism in guix packages, I want to encourage builders to build the 
manifest without substitutes.

I'd like to provide mostly distribution-agnostic documentation. Instructing 
builders to build a more recent version of guix from source would make this
process less accessible.

Questions:

1. Why does it attempt to build guile 3.0.7? The version of guile defined in
   the latest version of guix (or the time-machine pinned commit) is 3.0.9.

2. Is there a way to avoid having to build guile 3.0.7? (While still using
   the guix provided by the installer script as a starting point.)

3. If not, is it possible to skip the test phase for this specific package?

4. If not, is there anything I can do to make the tests less likely to fail?