ci: removed multiple unused CI scripts

ci/README.md

@@ -2,40 +2,11 @@
 
 This directory contains scripts for each build step in each build stage.
 
-### Running a Stage Locally
-
-Be aware that the tests will be built and run in-place, so please run at your own risk.
-If the repository is not a fresh git clone, you might have to clean files from previous builds or test runs first.
-
-The ci needs to perform various sysadmin tasks such as installing packages or writing to the user's home directory.
-While most of the actions are done inside a docker container, this is not possible for all. Thus, cache directories,
-such as the depends cache, previous release binaries, or ccache, are mounted as read-write into the docker container. While it should be fine to run
-the ci system locally on your development box, the ci scripts can generally be assumed to have received less review and
-testing compared to other parts of the codebase. If you want to keep the work tree clean, you might want to run the ci
-system in a virtual machine with a Linux operating system of your choice.
-
-To allow for a wide range of tested environments, but also ensure reproducibility to some extent, the test stage
-requires `docker` to be installed. To run on different architectures than the host `qemu` is also required. To install all requirements on Ubuntu, run
-
-```
-sudo apt install docker.io bash qemu-user-static
-```
-
-To run the default test stage,
-
-```
-./ci/test_run_all.sh
-```
-
-To run the test stage with a specific configuration,
-
-```
-FILE_ENV="./ci/test/00_setup_env_arm.sh" ./ci/test_run_all.sh
-```
-
 ### Configurations
 
-The test files (`FILE_ENV`) are constructed to test a wide range of
+Configurations live in `ci/test/00_setup_env*.sh` and are selected by
+`BUILD_TARGET` in `ci/dash/matrix.sh`, driven by the GitHub Actions workflows
+in `.github/workflows`. They are constructed to test a wide range of
 configurations, rather than a single pass/fail. This helps to catch build
 failures and logic errors that present on platforms other than the ones the
 author has tested.
@@ -45,18 +16,8 @@ the system package manager to install build dependencies. This guarantees that
 the tester is using the same versions as the release builds, which also use
 `./depends`.
 
-If no `FILE_ENV` has been specified or values are left out, `00_setup_env.sh`
-is used as the default configuration with fallback values.
-
-It is also possible to force a specific configuration without modifying the
-file. For example,
-
-```
-MAKEJOBS="-j1" FILE_ENV="./ci/test/00_setup_env_arm.sh" ./ci/test_run_all.sh
-```
-
-The files starting with `0n` (`n` greater than 0) are the scripts that are run
-in order.
+If values are left out, `00_setup_env.sh` is used as the default configuration
+with fallback values.
 
 ### Cache