[xen staging] CI: Turn debian/12-x86_64 into a non-root container

[patchbot@xxxxxxx]

commit 93f4d2da2221d1d8b39b2c0998b625f4c68ef769
Author:     Javi Merino <javi.merino@xxxxxxxxx>
AuthorDate: Tue Aug 12 16:47:34 2025 +0100
Commit:     Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
CommitDate: Tue Aug 12 20:17:25 2025 +0100

    CI: Turn debian/12-x86_64 into a non-root container
    
    Since commit 4611ae6fb8f9 ("CI: save toolstack artifact as cpio.gz"), the
    various automation/scripts/* no longer need to be root to correctly repack 
the
    initrd for test.
    
    Signed-off-by: Javi Merino <javi.merino@xxxxxxxxx>
    Signed-off-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
    Reviewed-by: Anthony PERARD <anthony.perard@xxxxxxxxxx>
---
 automation/build/debian/12-x86_64.dockerfile | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/automation/build/debian/12-x86_64.dockerfile 
b/automation/build/debian/12-x86_64.dockerfile
index e26a19079e..3cf99c730b 100644
--- a/automation/build/debian/12-x86_64.dockerfile
+++ b/automation/build/debian/12-x86_64.dockerfile
@@ -9,6 +9,8 @@ RUN <<EOF
 #!/bin/bash
     set -eu
 
+    useradd --create-home user
+
     apt-get update
 
     DEPS=(
@@ -70,5 +72,5 @@ RUN <<EOF
     rm -rf /var/lib/apt/lists*
 EOF
 
-USER root
+USER user
 WORKDIR /build
--
generated by git-patchbot for /home/xen/git/xen.git#staging