Test failure in p5332-multi-pack-reuse.sh

[Philippe Blain <levraiphilippeblain@gmail.com>]

Hi Taylor,

I noticed that p5332-multi-pack-reuse.sh, which you added in 
ba47d88795 (t/perf: add performance tests for multi-pack reuse,
2023-12-14) fails early on in the second test ("setup bitmaps for
1-pack scenario"). Since perf tests run with '--immediate', I do not
know if further tests in that file also fail. It is reproducible on macOS [1] as 
well as Linux [2] (I don't know if these logs are public though).

I also tested on Linux on version 2.44.0 which is the first release
in which this test was added, and it also failed similarily.

Sidenote: on GitHub CI, I could not demonstrate the failure on Linux
because all Linux jobs run in containers, and the images we use do 
not have Git installed, such that actions/checkout@v4 uses the GitHub
API to download the repository instead of cloning it [3]. This leads 
die_if_build_dir_not_repo from perf-lib.sh to fail with
"No $GIT_PERF_REPO defined, and your build directory is not a repo" [4].
We could fix that by installing the 'git' package before the 'actions/checkout'
step, but we would need to account for the different package managers of 
the distros we test on.

Cheers,

Philippe.

[1] https://github.com/phil-blain/git/actions/runs/14580975799/job/40897421311#step:4:896
[2] https://gitlab.com/phil-blain/git/-/jobs/9780586827#L2889
[3] https://github.com/phil-blain/git/actions/runs/14580975799/job/40897421399#step:4:28
[4] https://github.com/phil-blain/git/actions/runs/14580975799/job/40897421399#step:8:838