Restore PM-specific option specification in mock config

It appears that we actually WANT this configuration key to change with
the package manager, and this will be required as mock now supports
multiple DNF tools.

This reverts part of ed19495

ros_buildfarm/templates/release/rpm/mock_config.cfg.em

@@ -10,7 +10,11 @@ config_opts['use_bootstrap'] = False
 config_opts['chroot_setup_cmd'] += ' python3-rpm-macros'
 
 # Install weak dependencies to get group members
-config_opts[f'dnf_builddep_opts'] = config_opts.get(f'dnf_builddep_opts', []) + ['--setopt=install_weak_deps=True']
+config_opts[f'{config_opts.package_manager}_builddep_opts'] = config_opts.get(f'{config_opts.package_manager}_builddep_opts', []) + ['--setopt=install_weak_deps=True']
+
+# Deal with dnf -> dnf4 transition - see rpm-software-management/mock#1496
+if config_opts.package_manager == 'dnf':
+    config_opts[f'dnf4_builddep_opts'] = config_opts.get(f'dnf4_builddep_opts', []) + ['--setopt=install_weak_deps=True']
 
 @[if env_vars]@
 # Set environment vars from the build config