Fix capture-build-details.sh to work with detached state or tags

[dnzxy]

Fixes build so that Trio can be built from a detached state (single commit checked out) or tags.

Thank you @bjorkert 🙏

[marionbarker]

Status

Success

Tested building a detached HEAD

Background

Previously when checking out an earlier commit of a given branch and leaving it as a detached HEAD, the capture-build-details.sh failed when trying to build because there was no branch.

Test

Update local clone to

• 8811afe0 (dnzxy/fix-capture-build) Fix capture-build-details.sh to work with detached state or tags
• test that build succeeds
• add empty commit to advance the SHA for the branch (in local clone)

git commit --allow-empty -m "empty commit"

• checkout a detached HEAD pointing to 8811afe0

git checkout 8811afe0
xed .

Build was successful

• Trio, Settings indicates: branch: detached 8811afe

[bjornoleh]

Merging with two approvals.