drone: run apk fix when using alpine/git on ARM

[yvrhdn]

What this PR does:
Drone CI has been failing during the docker-arm image-tag step. Log from the Drone runner:

latest: Pulling from alpine/git
Digest: sha256:f73275dbb1a12e4322778e8d1cc7bda1656a849fb4b0e6b7fb935e8cf06c5cee
Status: Downloaded newer image for alpine/git:latest
+ apk --update --no-cache add bash
fetch https://dl-cdn.alpinelinux.org/alpine/v3.14/main/aarch64/APKINDEX.tar.gz
fetch https://dl-cdn.alpinelinux.org/alpine/v3.14/community/aarch64/APKINDEX.tar.gz
(1/2) Installing readline (8.1.0-r0)
(2/2) Installing bash (5.1.4-r0)
Executing bash-5.1.4-r0.post-install
Executing busybox-1.33.1-r3.trigger
1 error; 27 MiB in 34 packages

You can reproduce this by running alpine/git locally on a ARM machine:

$ docker run -it --entrypoint=/bin/sh alpine/git
/git # apk --update --no-cache add bash
fetch https://dl-cdn.alpinelinux.org/alpine/v3.14/main/aarch64/APKINDEX.tar.gz
fetch https://dl-cdn.alpinelinux.org/alpine/v3.14/community/aarch64/APKINDEX.tar.gz
(1/2) Installing readline (8.1.0-r0)
(2/2) Installing bash (5.1.4-r0)
Executing bash-5.1.4-r0.post-install
Executing busybox-1.33.1-r3.trigger
1 error; 27 MiB in 34 packages
/git # echo $?
1

By running apk fix before apk add we fix any broken installed packages:

$ docker run -it --entrypoint=/bin/sh alpine/git
/git # apk fix
fetch https://dl-cdn.alpinelinux.org/alpine/v3.14/main/aarch64/APKINDEX.tar.gz
fetch https://dl-cdn.alpinelinux.org/alpine/v3.14/community/aarch64/APKINDEX.tar.gz
(1/1) Reinstalling ca-certificates (20191127-r5)
Executing busybox-1.33.1-r3.trigger
Executing ca-certificates-20191127-r5.trigger
OK: 25 MiB in 32 packages
/git # apk --update --no-cache add bash
fetch https://dl-cdn.alpinelinux.org/alpine/v3.14/main/aarch64/APKINDEX.tar.gz
fetch https://dl-cdn.alpinelinux.org/alpine/v3.14/community/aarch64/APKINDEX.tar.gz
(1/2) Installing readline (8.1.0-r0)
(2/2) Installing bash (5.1.4-r0)
Executing bash-5.1.4-r0.post-install
Executing busybox-1.33.1-r3.trigger
OK: 27 MiB in 34 packages

Which issue(s) this PR fixes:
Fixes #

Checklist

• Tests updated
• Documentation added
• CHANGELOG.md updated - the order of entries should be [CHANGE], [FEATURE], [ENHANCEMENT], [BUGFIX]

[yvrhdn]

Filed an issue upstream: alpine-docker/git#35