Update base alpine image

[hydrargyrum]

When running trivy on this gitolite dockerhub image:

% docker run --rm -v /var/run/docker.sock:/var/run/docker.sock -v trivy-cache:/root/.cache/ aquasec/trivy i jgiannuzzi/gitolite
2021-07-30T21:31:51.732Z	INFO	Detected OS: alpine
2021-07-30T21:31:51.732Z	INFO	Detecting Alpine vulnerabilities...
2021-07-30T21:31:51.733Z	INFO	Number of language-specific files: 0
2021-07-30T21:31:51.733Z	WARN	This OS version is no longer supported by the distribution: alpine 3.10.1

[...]

It appears the base image alpine version (3.10) is not supported anymore by alpine (since 2021-05-01).

It would be safer to use a fresher alpine base image.

[hydrargyrum]

any news @jgiannuzzi ? 3.10 is not supported since 2021, alpine is now using 3.18, see https://alpinelinux.org/releases/

see also https://endoflife.date/alpine