[PATCH v1] automation: update documentation about how to build a container

[Olaf Hering <olaf@xxxxxxxxx>]

The command used in the example is different from the command used in
the Gitlab CI pipelines. Adjust it to simulate what will be used by CI.
This is essentially the build script, which is invoked with a number of
expected environment variables such as CC, CXX and debug.

In addition the input should not be a tty, which disables colors from
meson and interactive questions from kconfig.

Signed-off-by: Olaf Hering <olaf@xxxxxxxxx>
---
 automation/build/README.md | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/automation/build/README.md b/automation/build/README.md
index 2d07cafe0e..1c040533fd 100644
--- a/automation/build/README.md
+++ b/automation/build/README.md
@@ -96,7 +96,8 @@ docker login registry.gitlab.com/xen-project/xen
 make -C automation/build suse/opensuse-tumbleweed
 env CONTAINER_NO_PULL=1 \
   CONTAINER=tumbleweed \
-  automation/scripts/containerize bash -exc './configure && make'
+  CONTAINER_ARGS='-e CC=gcc -e CXX=g++ -e debug=y' \
+  automation/scripts/containerize automation/scripts/build < /dev/null
 make -C automation/build suse/opensuse-tumbleweed PUSH=1
 ```