CI: fix macos64 tests on Cirrus

[andy5995]

No description provided.

[andy5995]

I don't see yet why this is failing. The variable seems right. It must be because it works on the other two Cirrus tests.

https://github.com/netpanzer/netpanzer/runs/20645525949

I'll let it sit for now.

[andy5995]

On macos arm64 the test to get the data dir files because it doesn't match MESON_SOURCE_ROOT

On Cirrus->Ubuntu645:

stderr:
datadir: /tmp/cirrus-ci-build
meson_source_root: /tmp/cirrus-ci-build

On the mac:

datadir: /var/folders/n8/pp_chp6x3jlfy1n94r6hdjv40000gn/T/cirrus-ci-build
meson_source_root: /private/var/folders/n8/pp_chp6x3jlfy1n94r6hdjv40000gn/T/cirrus-ci-build

[andy5995]

I'm trying to get a little more info and started a discussion on LQ.