Install host-arch perl deps, force target arch git to use them

This does cause `git:s390x` to install in the s390x cross container
but the changes are not finished -- container creation still fails
due to a subsequent attempt to fix missing packages. Assuming `git`
can use `perl` from a different architecture, which seems likely
since it is invoking it as an interpreter (rather than linking to
it), this should be fine, but to limit container bloat some other
changes are needed to make it so we don't need the `autoremove`
operation to get rid of files only used in setting up the PPA.

Author: EliahKagan

etc/docker/Dockerfile.test-cross

@@ -15,10 +15,12 @@ RUN set -uC && \
     add-apt-repository -y ppa:git-core/ppa && \
     apt-get update && \
     apt-get install --no-install-recommends -y "libc6$apt_suffix" "libcurl3-gnutls$apt_suffix" \
-        "libexpat1$apt_suffix" "libpcre2-8-0$apt_suffix" "zlib1g$apt_suffix" "perl$apt_suffix" \
-        liberror-perl git-man patch jq && \
+        "libexpat1$apt_suffix" "libpcre2-8-0$apt_suffix" "zlib1g$apt_suffix" perl liberror-perl \
+        git-man patch jq && \
     apt-get download "git$apt_suffix" && \
-    dpkg --ignore-depends="liberror-perl$apt_suffix" -i ./git[-_]*.deb && \
+    dpkg --ignore-depends="perl$apt_suffix,liberror-perl$apt_suffix" -i git[-_]*.deb && \
+    echo INSTALLED/UPGRADED GIT && \
+    rm git[-_]*.deb && \
     apt-get purge --autoremove software-properties-common && \
     apt-get clean && \
     rm -rf /var/lib/apt/lists/* && \