bootstrap/cbuild: fix pkgcmd_prepare for Debian 9 (stretch) containers (again)
Debian 9 (stretch) is end of life, and the repositories are archived. We need to patch the sources.list file to be able to install packages.
The earlier attempts to patch "sources.list" for debian:9 were not correct and repositories were missing. Fix it, again.
Manual changes are only in "bootstrap/cbuild" file.
Fixes: 08fce249 ('bootstrap/cbuild: fix pkgcmd_prepare for Debian 9 (strech) containers')
I was again unable to test this. Trying to just use my gitlab-fork in .gitlab-ci/ci.template
somehow didn't work. And when I used the suggestion from !174 (comment 1925302) , it does not seem to work (the redirection gets quoted to ">>"). I cannot figure out how to do this right. On the other hand, the "echo" lines are exactly the same as a few lines above, so maybe will work(?).