Make the test image toolbox-ready

Adjust the Dockerfile a bit so that one can use it to build a toolbox
[*] image for developing rpm, like so:

    podman build --target base -t <tag> -f tests/Dockerfile .
    toolbox create -i <tag>
    toolbox enter <tag>

This is convenient since the image already contains all the dependencies
that one would have to install manually otherwise.

Specifically, add a podman shim (see the previous commit for details) so
that "make check" works as expected when run in a toolbox. While at it,
also install a couple of useful development tools.

Add a LABEL that marks the image as toolbox-ready, as per [*].

[*] https://containertoolbx.org/doc/

Author: dmnks

tests/Dockerfile.fedora

@@ -1,5 +1,6 @@
 # Supported Fedora releases: 41 42
 FROM registry.fedoraproject.org/fedora:42 AS base
+LABEL com.github.containers.toolbox="true"
 MAINTAINER rpm-maint@lists.rpm.org
 
 RUN echo -e "deltarpm=0\ninstall_weak_deps=0\ntsflags=nodocs" >> /etc/dnf/dnf.conf
@@ -61,8 +62,23 @@ RUN dnf -y install \
 RUN rm -f /usr/lib/rpm/macros.d/macros.transaction_ima
 # If updates to specific packages are needed, do it here
 RUN dnf -y --enablerepo=rawhide install "sequoia-sq >= 1.3" "rpm-sequoia >= 1.9" "crypto-policies >= 20250402"
+
+# Install some development tools
+RUN dnf -y install \
+    flatpak-spawn \
+    gdb \
+    strace \
+    valgrind
+
 RUN dnf clean all
 
+# Install podman shim for use in toolbox containers
+RUN cat <<EOF > /usr/local/bin/podman
+#!/bin/bash
+exec flatpak-spawn --host podman "\$@"
+EOF
+RUN chmod +x /usr/local/bin/podman
+
 # Workaround for pkgconf(1)'s unlisted dependency on rpm.
 # This is needed for cmake to work without an rpm installation.
 RUN ln -sf $(rpm --eval '%{_target_platform}%{?_gnu}')-pkg-config \