Tool for running Scheme tests with different implementations in Docker

Uses [compile-r7rs](https://codeberg.org/retropikzel/compile-r7rs) internally.

It assumes you have docker installed and configured so that it does not need sudo.

- If testfile ends in .sps then akku-r7rs is also installed which allows running
R7RS code on R6RS implementations
- Set APT_PACKAGES environment variable to list of apt (Debian) packages you
want installed inside the Docker container
- Set SNOW_PACKAGES environment variable to list of snow-fort packages you
want installed inside the Docker container
    - Use the dot format! So for example retropikzel.system and NOT (retropikzel system)
    - You can also list .tgz packages in local dir
- Set AKKU_PACKAGES environment variable to list of Akku packages you
want installed inside the Docker container
- To pass environment values into container add their name into environment
variable PASS_ENV_VARS
- To see debug output set environment variable TEST_R7RS_DEBUG
- To change docker tag set environment variable DOCKER_TAG
    - Default is latest, you might want to also try head
    - Note that only debian based tags are supported for now

## Installation

    snow-chibi install --impls=chibi retropikzel.test-r7rs

## Usage

    COMPILE_R7RS=${SCHEME} test-r7rs main.scm

## Usage with additional load paths

    COMPILE_R7RS=${SCHEME} test-r7rs -o main -I libs -A other_libs main.scm

## Usage with library snowball that needs to be installed first

    snow-chibi package libs/foo/bar.sld
    SNOW_PACKAGES="foo-bar.tgz" COMPILE_R7RS=${SCHEME} test-r7rs -o main main.scm

## Supported implementations

Same as compile-r7rs.