The version of simple-scan that current in Guix, 3.24.1, which fails to 
build is a little old. I tried to update it to the version that 
numerically matches our GNOME version, 3.30.2, but that fails with the 
same problem.

However, the current newest simple-scan release, 3.34.1, does build. 
Unfortunately, I had to take the colord out of inputs or native inputs 
otherwise the build would fail with

"error: Package `colord' not found in specified Vala API directories or 
GObject-Introspection GIR directories"

and I didn't see how it was detecting colord during configure, but not 
during the build. The needs to be fixed eventually, but in the meantime I 
have prepared the following patch.

A bigger problem than colord though, is that while simple-scan now builds, 
it doesn't run. It exits after printing "Trace/breakpoint trap". I've 
attached strace output.

I'm not sure what's next, thoughts?

Best,
Jack