Review build labelling convention for alpine-linux agent build labels

[sxa]

          Noting that https://ci.adoptium.net/job/build-scripts/job/jobs/job/jdk17u/job/jdk17u-alpine-linux-x64-temurin/393/ and the equivalent on other versions appears to insist on running on one of the equinix dockerhosts at the moment as it's looking for `build&&alpine-linux&&x64&&dockerBuild` - we'll need to think about that labelling convention ...

23:30:52  [NODE SHIFT] MOVING INTO DOCKER NODE MATCHING LABELNAME build&&alpine-linux&&x64&&dockerBuild...
[Pipeline] node
23:31:07  Still waiting to schedule task
23:31:07  ‘[dockerhost-equinix-ubuntu2204-x64-1](https://ci.adoptium.net/computer/dockerhost%2Dequinix%2Dubuntu2204%2Dx64%2D1/)’ is offline
23:59:27  Running on [dockerhost-equinix-ubuntu2204-x64-1](https://ci.adoptium.net/computer/dockerhost%2Dequinix%2Dubuntu2204%2Dx64%2D1/) in /home/jenkins/workspace/build-scripts/jobs/jdk17u/jdk17u-alpine-linux-x64-temurin
[Pipeline] {

Originally posted by @sxa in #3352 (comment)

It seems that unless the build dockerhost has alpine-linux in the labels (which is misleading - it's not alpine - the alpine builds cannot be scheduled on it. We should look at whether there is a more sensible way to do this. Noting that I temporarily enabled the equinix machine which has this label in order to allow the builds to progress tonight.