add docker-helper.sh to lift examples using pac-nix docker image (#514)

this introduces the src/test/make/docker-helper.sh script which is
a (hopefully) developer-friendly method for lifting examples in a Docker
container provided by [pac-nix][].

to ensure reproducibility, this uses an x86_64-linux docker container
with cross-compiler provided by nix. for more details, see #288 which
the
docker-helper.sh is stolen from.

the usage is comprehensively documented in [readme].
the general flow is:
1. activate the docker-helper.sh environment: `eval $(docker-helper.sh
env)`.
   (you will need to re-run this if you close your terminal)
2. pull the docker image: `docker-helper.sh pull`
3. start the docker container: `docker-helper.sh start`
4. (optional) clean the directory you want to lift:
`make SUBDIRS=extraspec_incorrect/malloc_memcpy_strlen_memset_free
clean`
5. compile and lift the directory:
   `make SUBDIRS=extraspec_incorrect/malloc_memcpy_strlen_memset_free`
6. commit the results (eventually, we want to move the binaries into
an out-of-repo location. but until then, committing is probably fine.)

[pac-nix]: https://github.com/katrinafyi/pac-nix/
[readme]:
https://github.com/UQ-PAC/BASIL/blob/docker-helper/src/test/readme.md

this PR does not make any changes to the existing examples. it only
serves to make the Docker container available and accessible for people
who want to use it as a uniform lifting environment.

I do think that all examples should eventually be re-lifted using a
consistent method, but this will come later.

Author: katrinafyi

.gitattributes

@@ -1,3 +1,11 @@
 *.mill linguist-language=Scala
 mill linguist-generated
 mill.bat linguist-generated
+
+src/test/compiled.url.txt text eol=lf
+src/test/make/docker-flake.txt text eol=lf
+
+Makefile text eol=lf
+*.sh text eol=lf
+*.mk text eol=lf
+*.md5sum text eol=lf linguist-generated

.github/workflows/check-doc-links.sh

@@ -32,6 +32,8 @@ args=(
   --insecure
   --no-progress
   --max-concurrency 16
+  --max-retries 10
+  --timeout 40
   "$@"
 )
 

docs/src/SUMMARY.md

@@ -31,6 +31,7 @@
 # Devleopment Guidelines
 
 - [Testing](development/testing.md)
+  - [Integration (system) tests](development/integration-tests.md)
 - [Assertions](development/assertions.md)
 - [Scala](development/scala.md)