fix: faster installation of custom RPMs

Thanks to leveraging Bash arrays, we are now able to use parameter expansion to perform every package installation as one rpm-ostree operation instead of individual ones. This will give us a huge build speedup.

Bash properly expands every array element as safely quoted arguments, complete with support for spaces and special characters.

build.sh

@@ -36,10 +36,8 @@ rpm-ostree override remove firefox firefox-langpacks
 get_yaml_array install_rpms '.rpms[]'
 if [[ ${#install_rpms[@]} -gt 0 ]]; then
     echo "-- Installing RPMs defined in recipe.yml --"
-    for pkg in "${install_rpms[@]}"; do
-        echo "Installing: ${pkg}"
-        rpm-ostree install $pkg
-    done
+    echo "Installing: ${install_rpms[@]}"
+    rpm-ostree install "${install_rpms[@]}"
     echo "---"
 fi