build.sh: add CentOS Stream keys into /etc/pki/rpm-gpg

This goes together with a related patch in openshift/os. Copying the
same context from that one:

A long-standing issue that rears its head in various places in our
code is the fact that the repo files for CentOS Stream reference a
`gpgkey` path that is valid only for cosa but not within a CentOS Stream
environment. See e.g. 0a7ad3b ("extensions: Workaround for CentOS GPG
key paths") in the openshift/os repo for an example issue.

We don't have this problem with RHEL because cosa, being Fedora-based,
ships the Red Hat key in its `/etc/pki/rpm-gpg`. I want to address this
for CentOS Stream the same way, i.e. by adding the CentOS Stream keys to
`/etc/pki/rpm-gpg` in cosa. This should allow us to simplify code there.

Author: jlebon

build.sh

@@ -90,6 +90,17 @@ install_rpms() {
     fi
     # Similarly for kernel data and SELinux policy, which we want to inject into supermin
     chmod -R a+rX /usr/lib/modules /usr/share/selinux/targeted
+
+    # Symlink the CentOS Stream GPG keys to /etc to make it easier to build
+    # CentOS-based artifacts.
+    if [ ! -e "/etc/pki/rpm-gpg/RPM-GPG-KEY-centosofficial" ]; then
+        ln -s /usr/share/distribution-gpg-keys/centos/RPM-GPG-KEY-CentOS-Official /etc/pki/rpm-gpg/RPM-GPG-KEY-centosofficial
+        ln -s {/usr/share/distribution-gpg-keys/centos,/etc/pki/rpm-gpg}/RPM-GPG-KEY-CentOS-SIG-Cloud
+        ln -s {/usr/share/distribution-gpg-keys/centos,/etc/pki/rpm-gpg}/RPM-GPG-KEY-CentOS-SIG-Extras-SHA512
+        ln -s {/usr/share/distribution-gpg-keys/centos,/etc/pki/rpm-gpg}/RPM-GPG-KEY-CentOS-SIG-NFV
+        ln -s {/usr/share/distribution-gpg-keys/centos,/etc/pki/rpm-gpg}/RPM-GPG-KEY-CentOS-SIG-Virtualization
+    fi
+
     # Further cleanup
     yum clean all
 }