Upgrade CI images to Ubuntu 22

This updates all images in the CI to Ubuntu 22. It also updates
corresponding documentation. Remove python(2) from the image, as it is
not needed. Update documentation.

It seems that the gcc coming in Ubuntu 22 does not like
stack-protector-strong, so remove it as well.

Since we compile Flexric, which does not support Ubuntu 22's default
gcc-11 (it hits a compile bug), switch to gcc-12 manually.

Since we update the compiler, we also need to be careful to use the right
address sanitizer version (which is bundled with the compiler version).
To avoid a reinstallation of the wrong asan version in target images, we
modify Ubuntu 22 targets to copy libasan from the base image. This is necessary
since we use update-alternative in the base image, but we don't want to
install compilers in the target images to use update-alternatives to
install the right asan version... This should be undone when switching
to Ubuntu 24 in the future, as it will have a newer default gcc version,
such that we don't need to update the compile in the first place.

Upgrade libpython in lteUE for U22 upgrade to make it compatible with
UHD.

docker/README.md

@@ -75,18 +75,18 @@ Targets can be:
 The currently-supported OS are:
 
 - `rhel9` for Red Hat Entreprise Linux (including images for an OpenShift cluster)
-- `ubuntu20` for Ubuntu 20.04 LTS
+- `ubuntu22` for Ubuntu 22.04 LTS
 - `rocky` for Rocky-Linux 8.7
 
 For more details regarding the build on an Openshift Cluster, see [OpenShift README](../openshift/README.md).
 
-# 3. Building using `docker` under Ubuntu 20.04 #
+# 3. Building using `docker` under Ubuntu 22.04 #
 
 ## 3.1. Pre-requisites ##
 
 * `git` installed
 * `docker-ce` installed
-* Pulling `ubuntu:focal` from DockerHub
+* Pulling `ubuntu:jammy` from DockerHub
 
 ## 3.2. Building the shared images ##
 
@@ -96,8 +96,8 @@ There are two shared images: one that has all dependencies, and a second that co
 git clone https://gitlab.eurecom.fr/oai/openairinterface5g.git
 cd openairinterface5g
 git checkout develop
-docker build --target ran-base --tag ran-base:latest --file docker/Dockerfile.base.ubuntu20 .
-docker build --target ran-build --tag ran-build:latest --file docker/Dockerfile.build.ubuntu20 .
+docker build --target ran-base --tag ran-base:latest --file docker/Dockerfile.base.ubuntu22 .
+docker build --target ran-build --tag ran-build:latest --file docker/Dockerfile.build.ubuntu22 .
 ```
 
 After building both:
@@ -115,12 +115,12 @@ Note that the steps are identical for `rocky-linux`.
 
 ### 3.2.1. Additional build otions
 
-This is only available for the Ubuntu-20 version.
+This is only available for the Ubuntu version of Dockerfiles.
 
 You can, for example, create a `sanitizer` version of the ran-build image.
 
 ```bash
-docker build --target ran-build --tag ran-build:latest --file docker/Dockerfile.build.ubuntu20 --build-arg "BUILD_OPTION=--sanitize" .
+docker build --target ran-build --tag ran-build:latest --file docker/Dockerfile.build.ubuntu22 --build-arg "BUILD_OPTION=--sanitize" .
 ```
 
 Currently the `--sanitize` option for `build_oai` enables:
@@ -146,7 +146,7 @@ You can also use this docker build arguments to pass any available option(s) on
 For example, the eNB:
 
 ```bash
-docker build --target oai-enb --tag oai-enb:latest --file docker/Dockerfile.eNB.ubuntu20 .
+docker build --target oai-enb --tag oai-enb:latest --file docker/Dockerfile.eNB.ubuntu22 .
 ```
 
 After a while:
@@ -171,7 +171,7 @@ Note that the steps are identical for `rocky-linux`.
 If you have used the sanitizer option, then you should also pass it when building the target image:
 
 ```bash
-docker build --target oai-gnb --tag oai-gnb:latest --file docker/Dockerfile.gNB.ubuntu20 --build-arg "BUILD_OPTION=--sanitize" .
+docker build --target oai-gnb --tag oai-gnb:latest --file docker/Dockerfile.gNB.ubuntu22 --build-arg "BUILD_OPTION=--sanitize" .
 ```
 
 Normally the target image will be around 200 Mbytes bigger.