fetch-cache: Use target distro and arch

We where using host ditro / arch, which would result in the wrong cache
being pulled.
3 jobs for fix-fetch-cache in 50 minutes and 14 seconds (queued for 2 seconds)
Status Job ID Name Coverage
  Preparation
passed #66426
manifest

00:00:19

 
  Build
passed #66427
cerbero deps fedora x86_64

00:39:27

 
  Full Builds
passed #66428
build cerbero fedora x86_64

00:10:28