configure: allow user to override docker engine

If you have both engines installed but one is broken you are stuck
with the automagic. Allow the user to override the engine for this
case.

Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
Reviewed-by: Alistair Francis <alistair.francis@wdc.com>
Message-Id: <20231009164104.369749-7-alex.bennee@linaro.org>

configure

@@ -180,6 +180,7 @@ fi
 # some defaults, based on the host environment
 
 # default parameters
+container_engine="auto"
 cpu=""
 cross_compile="no"
 cross_prefix=""
@@ -787,6 +788,8 @@ for opt do
   ;;
   --disable-containers) use_containers="no"
   ;;
+  --container-engine=*) container_engine="$optarg"
+  ;;
   --gdb=*) gdb_bin="$optarg"
   ;;
   # everything else has the same name in configure and meson
@@ -921,6 +924,7 @@ Advanced options (experts only):
   --enable-plugins
                            enable plugins via shared library loading
   --disable-containers     don't use containers for cross-building
+  --container-engine=TYPE  which container engine to use [$container_engine]
   --gdb=GDB-path           gdb to use for gdbstub tests [$gdb_bin]
 EOF
   meson_options_help
@@ -1195,14 +1199,14 @@ fi
 container="no"
 runc=""
 if test $use_containers = "yes" && (has "docker" || has "podman"); then
-    case $($python "$source_path"/tests/docker/docker.py probe) in
+    case $($python "$source_path"/tests/docker/docker.py --engine "$container_engine" probe) in
         *docker) container=docker ;;
         podman) container=podman ;;
         no) container=no ;;
     esac
     if test "$container" != "no"; then
         docker_py="$python $source_path/tests/docker/docker.py --engine $container"
-        runc=$($python "$source_path"/tests/docker/docker.py probe)
+        runc=$container
     fi
 fi