Add Alpine variant

[J0WI]

This adds a php-fpm-alpine variant with the same dependencies installed as the Debian variants, but without Cron (#253). The entrypoint.sh is not fully POSIX compatible, so there are some extra dependencies for it.

[J0WI]

Only 64-bit works so far. @tianon do you know how I can build APCu on 32-bit?

[tilosp]

I think you should merge the top 3 RUN commands into a single one to keep it a similar as possible to the debian one.

[J0WI]

This way is better for build caching. See also other images in the docker-library.
I can adjust the Debian images if required.

[tilosp]

We have to get this to build on other platforms than amd64.
@tianon and @yosifkit any idea?

[tilosp]

we should also update generate-stackbrew-library.sh similar to docker-library/wordpress#223 because debian supports different architectures than alpine.

[tianon]

/usr/local/include/php/ext/pcre/php_pcre.h:29:18: fatal error: pcre.h: No such file or directory

Adding pcre-dev to .build-deps appears to get past that error on i386.

[tianon]

(https://ram.tianon.xyz/post/2017/12/26/dockerize-compiled-software.html is a writeup about how I usually solve this type of issue generally when Dockerizing software)

[J0WI]

trigger Travis again

[J0WI]

Travis is not building for some reason.

@tianon thanks for the hint. But I'm still confused why this is working on amd64 without pcre-dev.

we should also update generate-stackbrew-library.sh similar to docker-library/wordpress#223 because debian supports different architectures than alpine.

I think this is not related to this PR. I'd like to add only Alpine images here.

[J0WI]

Travis is done now. Only fetching from keyserver failed once, which is acceptable.

[tilosp]

I think this is not related to this PR. I'd like to add only Alpine images here.

It is related to this pr. If we merge this now the Jenkins server will try to build the alpine variant on arm32v5 and arm32v7 which will fail because there is no base image.

[J0WI]

Okay, I can do this. But the bashbrew dependency makes it a bit tricky. I didn't found a proper way to add bashbrew to Travis, but I don't want to hardcode the architectures again.

[tianon]

FWIW, up-to-date pre-built binaries of bashbrew can be found at https://doi-janky.infosiftr.net/job/bashbrew/lastSuccessfulBuild/artifact/bin/

[J0WI]

@tilosp can you help me out with the bashbrew dependency on Travis?

[J0WI]

@tilosp thanks for fixing it. I would like to request a review again.

[tilosp]

@J0WI i added the cron.sh. This adds only 62 Bytes.

[tilosp]

LGTM

[tilosp]

@tianon please review

[tilosp]

Thanks a lot for your work!