Work around 'podman exec' resetting the terminal size to 80x24

See: containers/podman#3946

COLUMNS and LINES may not be set in the user's environment. Hence the
existing mechanism for preserving environment variables don't work.

Note that for things to keep working when invoked via D-Bus from
inside a toolbox container, the terminal size needs to be queried using
the standard input stream, instead of explicitly mentioning the
controlling terminal device /dev/tty. This is because stty(1) doesn't
have the notion of a controlling terminal when invoked via D-Bus, but
flatpak-spawn(1) ensures that the standard input stream still points
to the user's interactive terminal.

https://github.com/debarshiray/toolbox/issues/242

toolbox

@@ -322,7 +322,28 @@ create_enter_command()
 
 
 create_environment_options()
-{
+(
+    columns=""
+    lines=""
+
+    if terminal_size=$(stty size 2>&3); then
+        columns=$(echo "$terminal_size" | cut --delimiter " " --fields 2 2>&3)
+        if ! is_integer "$columns"; then
+            echo "$base_toolbox_command: failed to parse the number of columns from the terminal size" >&3
+            columns=""
+        fi
+
+        lines=$(echo "$terminal_size" | cut --delimiter " " --fields 1 2>&3)
+        if ! is_integer "$lines"; then
+            echo "$base_toolbox_command: failed to parse the number of lines from the terminal size" >&3
+            lines=""
+        fi
+
+        environment_options="$environment_options --env=COLUMNS=$columns --env=LINES=$lines"
+    else
+        echo "$base_toolbox_command: failed to read terminal size" >&3
+    fi
+
     echo "$environment_variables" \
         | sed "s/ \+/\n/g" 2>&3 \
         | {
@@ -339,12 +360,20 @@ create_environment_options()
                   fi
               done
 
+              if [ "$columns" != "" ] 2>&3; then
+                  environment_options="$environment_options --env=COLUMNS=$columns"
+              fi
+
+              if [ "$lines" != "" ] 2>&3; then
+                  environment_options="$environment_options --env=LINES=$lines"
+              fi
+
               environment_options=${environment_options#" "}
               echo "$base_toolbox_command: created options for environment variables to forward" >&3
               echo "$environment_options" >&3
               echo "$environment_options"
           }
-}
+)
 
 
 create_toolbox_container_name()