RFR: Add Dockerfile, zero-dep reproducible builds

[Gavin Ray]

On Wed, 21 Sep 2022 13:55:19 GMT, Gavin Ray <duke at openjdk.org> wrote:

> As title says, adds a Dockerfile that will fetch all necessary deps and build `jextract` for you on Ubuntu 22.10
> 
> It would be nice if some official JDK organization could put this on their Dockerhub, so that users could just do:
> 
> 
> $ docker run --rm -it openjdk/jextract:latest
> 
> 
> I've pushed it to my personal Dockerhub, so if anyone would like to test it out, you can use the README directions but prepend `gavinray/` before the image name:
> 
> 
> $ echo "struct Foo { int a; long b; }; int use_foo(struct Foo foo);" >> sample.h
> 
> $ docker run --rm -it -v ${PWD}:/tmp/jextract \
>     gavinray/jextract:latest \
>     -I /tmp/jextract \
>     --source \
>     -l libfoo \
>     --output /tmp/jextract/generated \
>     --target-package com.example \

I signed the Oracle OCA for contributing to GraalVM already =/

https://github.com/oracle/graal/pull/3603#issuecomment-889122954

![image](https://user-images.githubusercontent.com/26604994/191549087-80e19bf3-becf-4b67-8175-ac608dd803c1.png)

But you already have my OCA, since last year ;..;

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PR: https://git.openjdk.org/jextract/pull/74