test/system: Ensure that $HOME is used as a fallback working directory

This needs a directory that's going to be present on the host operating
system across various configurations of all supported distributions,
such as the hosts running the CI, but not inside the Toolbx containers.

It looks like /etc/kernel is present on both Debian and Fedora, but
absent from the fedora-toolbox images.  On a Debian 10 server, it's
owned by several packages:
  $ dpkg-query --search /etc/kernel
  dkms, systemd, grub2-common, initramfs-tools, apt: /etc/kernel

... while on Fedora 36 Workstation:
  $ rpm --file --query /etc/kernel
  systemd-udev-250.8-1.fc36.x86_64

Currently, there's no way to get assert_line to use the stderr_lines
array [1].  This is worked around by assigning stderr_lines to the
'lines' array.

[1] https://github.com/bats-core/bats-assert/issues/42

https://github.com/containers/toolbox/pull/1153

test/system/104-run.bats

@@ -58,6 +58,23 @@ teardown() {
   assert_line --index $((${#lines[@]}-1)) "Hello World"
 }
 
+@test "run: Ensure that $HOME is used as a fallback working directory" {
+  local default_container_name="$(get_system_id)-toolbox-$(get_system_version)"
+  create_default_container
+
+  pushd /etc/kernel
+  run --separate-stderr $TOOLBOX run pwd
+  popd
+
+  assert_success
+  assert_line --index 0 "$HOME"
+  assert [ ${#lines[@]} -eq 1 ]
+  lines=("${stderr_lines[@]}")
+  assert_line --index $((${#stderr_lines[@]}-2)) "Error: directory /etc/kernel not found in container $default_container_name"
+  assert_line --index $((${#stderr_lines[@]}-1)) "Using $HOME instead."
+  assert [ ${#stderr_lines[@]} -gt 2 ]
+}
+
 @test "run: Try to run a command in the default container with no containers created" {
   local default_container_name="$(get_system_id)-toolbox-$(get_system_version)"