Add new sudo-cwd.sh - partial cherry-pick from main branch.

sudo-cwd.sh was developed on the main branch for zephyr but now we
want to re-use it for building topologies. Cherry-pick only that
script, not the zephyr parts.

Original commit message:

Besides making things more obvious, the important functional change is
that the user switch is now performed for _every_ invoked, command, not
just for the build command.

Signed-off-by: Marc Herbert <marc.herbert@intel.com>
(cherry picked from commit 027be98)

Author: marc-hb

scripts/sudo-cwd.sh

@@ -0,0 +1,73 @@
+#!/bin/sh
+# SPDX-License-Identifier: BSD-3-Clause
+# Copyright(c) 2022 Intel Corporation. All rights reserved.
+
+# This is a "brute force" solution to filesystem permission issues:
+#
+# If the current user does not own the current directory then this
+# wrapper script switches to the user who does own the current directory
+# before running the given command.
+
+# If no user owns the current directory, a user who does gets created
+# first!
+
+# The main use case is to run this first thing inside a container to
+# solve file ownership mismatches.
+
+# `docker run --user=$(id -un) ...` achieves something very similar
+# without any code except the resulting user many not exist inside the
+# container. Some commands may not like that.
+#
+# To understand more about the Docker problem solved here take a look at
+# https://stackoverflow.com/questions/35291520/docker-and-userns-remap-how-to-manage-volume-permissions-to-share-data-betwee
+# and many other similar questions.
+
+# TODO: replace sudo with gosu?
+
+set -e
+set -x
+
+# TODO: rename the "sof_" bits
+
+main()
+{
+    sof_uid="$(stat --printf='%u' .)"
+    local current_uid; current_uid="$(id -u)"
+    if test "$current_uid" = "$sof_uid"; then
+        exec "$@"
+    else
+        exec_as_sof_uid "$@"
+    fi
+}
+
+exec_as_sof_uid()
+{
+    # Add new container user matching the host user owning the SOF
+    # checkout
+    local sof_user; sof_user="$(id "$sof_uid")" || {
+        sof_user=sof_zephyr_docker_builder
+
+        local sof_guid; sof_guid="$(stat --printf='%g' .)"
+
+        getent group "$sof_guid" ||
+            sudo groupadd -g  "$sof_guid" sof_zephyr_docker_group
+
+        sudo useradd -m -u "$sof_uid" -g "$sof_guid" "$sof_user"
+
+        local current_user; current_user="$(id -un)"
+
+        # Copy sudo permissions just in case the build needs it
+        sudo sed -e "s/$current_user/$sof_user/" /etc/sudoers.d/"$current_user" |
+            sudo tee -a /etc/sudoers.d/"$sof_user"
+        sudo chmod --reference=/etc/sudoers.d/"$current_user" \
+             /etc/sudoers.d/"$sof_user"
+    }
+
+    # Double sudo to work around some funny restriction in
+    # zephyr-build:/etc/sudoers: 'user' can do anything but... only as
+    # root.
+    sudo sudo -u "$sof_user" REAL_CC="$REAL_CC" "$@"
+    exit "$?"
+}
+
+main "$@"