[CI][C++] Meson build is broken: File fixed_shape_tensor_test.cc does not exist

[kou]

Describe the bug, including details regarding any error messages, version, and platform.

https://github.com/apache/arrow/actions/runs/22696281103/job/65803283099#step:6:531

../../arrow/cpp/src/arrow/extension/meson.build:27:6: ERROR: File fixed_shape_tensor_test.cc does not exist.

#38008 may be related.

Component(s)

C++, Continuous Integration

[kou]

@WillAyd Could you take a look at this?

[WillAyd]

No problem - I'll address over the weekend