Fix several Alpine build issues related to ELF parsing

[qlyoung]

Several issues:

1. libelf-dev dependency was not added to APKBUILD.in for Alpine packaging
2. Our Alpine base image was using the latest tag, which is unstable and not appropriate for us
3. Once libelf-dev is added, our FRR Alpine images no longer build because libelf-dev hasn't been available in Alpine since 3.9; work around this by adding 3.9 Alpine repository to the 3.13 base image before building FRR

Fixes: #8489

[LabN-CI]

Outdated results 💚

Basic BGPD CI results: SUCCESS, 0 tests failed

_	_
Result	SUCCESS git merge/8491 3df81c2
Date	04/15/2021
Start	19:57:12
Finish	20:38:29
Run-Time	41:17
Total	1815
Pass	1815
Fail	0
Valgrind-Errors	0
Valgrind-Loss	0
Details	vncregress-2021-04-15-19:57:12.txt
Log	autoscript-2021-04-15-19:58:21.log.bz2
Memory	496 488 431

For details, please contact louberger

[NetDEF-CI]

Continuous Integration Result: SUCCESSFUL

Continuous Integration Result: SUCCESSFUL

Congratulations, this patch passed basic tests

Tested-by: NetDEF / OpenSourceRouting.org CI System

CI System Testrun URL: https://ci1.netdef.org/browse/FRR-FRRPULLREQ-18434/

This is a comment from an automated CI system.
For questions and feedback in regards to this CI system, please feel free to email
Martin Winter - mwinter (at) opensourcerouting.org.

[wesl-ee]

I don't think this is related to this change (I mean, Alpine was broken before so this is a needed fix) but I get this on starting a built container now:

w@kvm-gentoo ~/code/frr $ ./docker/alpine/build.sh
[...]
w@kvm-gentoo ~/code/frr $ docker run -it frr:alpine-3df81c2e10
cannot run start: /etc/frr/daemons does not exist

I can go in and inspect the container and see that /etc/frr is a regular file, not a directory.

w@kvm-gentoo ~/code/frr $ docker run --entrypoint /bin/bash -it frr:alpine-3df81c2e10
bash-5.1# ls /etc -l |grep frr
-rw-r--r--    1 root     root          2619 Apr 16 02:10 frr

The file is just an /etc/frr/daemons file

bash-5.1# cat /etc/frr 
# This file tells the frr package which daemons to start.
#
# Sample configurations for these daemons can be found in
# /usr/share/doc/frr/examples/.
[...]

Just curious if you can build & run or if my docker is playing tricks with me.

[eqvinox]

3. Once `libelf-dev` is added, our FRR Alpine images no longer build because `libelf-dev` hasn't been available in Alpine since 3.9; work around this by adding 3.9 Alpine repository to the 3.13 base image before building FRR

The correct package seems to be elfutils-dev (https://git.alpinelinux.org/aports/tree/main/elfutils/APKBUILD?h=3.13-stable)

[qlyoung]

Right you are...couldn't find that anywhere

[LabN-CI]

💚 Basic BGPD CI results: SUCCESS, 0 tests failed

Results table

_	_
Result	SUCCESS git merge/8491 9513086
Date	04/16/2021
Start	13:05:44
Finish	13:46:52
Run-Time	41:08
Total	1815
Pass	1815
Fail	0
Valgrind-Errors	0
Valgrind-Loss	0
Details	vncregress-2021-04-16-13:05:44.txt
Log	autoscript-2021-04-16-13:06:50.log.bz2
Memory	505 484 429

For details, please contact louberger

[NetDEF-CI]

Continuous Integration Result: FAILED

Continuous Integration Result: FAILED

See below for issues.
CI System Testrun URL: https://ci1.netdef.org/browse/FRR-FRRPULLREQ-18441/

This is a comment from an automated CI system.
For questions and feedback in regards to this CI system, please feel free to email
Martin Winter - mwinter (at) opensourcerouting.org.

Get source / Pull Request: Successful

Building Stage: Successful

Basic Tests: Failed

Topotests Ubuntu 18.04 arm8 part 1: Failed (click for details)

Topotests Ubuntu 18.04 arm8 part 1: No useful log found

Successful on other platforms/tests

• Addresssanitizer topotests part 7
• Topotests Ubuntu 18.04 arm8 part 9
• Topotests Ubuntu 18.04 arm8 part 4
• Static analyzer (clang)
• Addresssanitizer topotests part 5
• Topotests Ubuntu 18.04 amd64 part 7
• Topotests Ubuntu 18.04 amd64 part 9
• Topotests Ubuntu 16.04 i386 part 2
• Fedora 29 rpm pkg check
• Topotests Ubuntu 18.04 arm8 part 5
• Topotests Ubuntu 18.04 arm8 part 0
• Addresssanitizer topotests part 0
• Addresssanitizer topotests part 4
• Topotests Ubuntu 18.04 amd64 part 4
• Ubuntu 18.04 deb pkg check
• Topotests Ubuntu 18.04 amd64 part 1
• Topotests Ubuntu 16.04 i386 part 5
• Topotests Ubuntu 16.04 i386 part 7
• CentOS 7 rpm pkg check
• Topotests Ubuntu 18.04 amd64 part 2
• IPv6 protocols on Ubuntu 18.04
• Topotests Ubuntu 18.04 amd64 part 0
• Topotests Ubuntu 18.04 arm8 part 3
• Topotests Ubuntu 18.04 amd64 part 3
• Addresssanitizer topotests part 1
• Topotests Ubuntu 18.04 arm8 part 8
• Topotests Ubuntu 18.04 arm8 part 6
• IPv4 protocols on Ubuntu 18.04
• Topotests Ubuntu 16.04 i386 part 0
• Addresssanitizer topotests part 8
• Debian 10 deb pkg check
• Topotests Ubuntu 16.04 i386 part 9
• Topotests Ubuntu 16.04 i386 part 1
• Topotests Ubuntu 16.04 i386 part 8
• Ubuntu 16.04 deb pkg check
• Addresssanitizer topotests part 6
• Topotests Ubuntu 18.04 amd64 part 6
• Topotests Ubuntu 18.04 amd64 part 5
• IPv4 ldp protocol on Ubuntu 18.04
• Addresssanitizer topotests part 2
• Ubuntu 20.04 deb pkg check
• Debian 9 deb pkg check
• Addresssanitizer topotests part 3
• Topotests Ubuntu 16.04 i386 part 3
• Topotests Ubuntu 18.04 amd64 part 8
• Topotests Ubuntu 18.04 arm8 part 2
• Addresssanitizer topotests part 9
• Topotests Ubuntu 18.04 arm8 part 7
• Topotests Ubuntu 16.04 i386 part 4
• Topotests Ubuntu 16.04 i386 part 6

[qlyoung]

ci:rerun

[NetDEF-CI]

Continuous Integration Result: SUCCESSFUL

Congratulations, this patch passed basic tests

Tested-by: NetDEF / OpenSourceRouting.org CI System

CI System Testrun URL: https://ci1.netdef.org/browse/FRR-FRRPULLREQ-18453/

This is a comment from an automated CI system.
For questions and feedback in regards to this CI system, please feel free to email
Martin Winter - mwinter (at) opensourcerouting.org.

[eqvinox]

Merging, since it was b0rked before this can't make it worse ;)