contrib: meson: always use meson `setup`

"meson builddir" has been deprecated since 0.64.0.

Please see 3c7ab542c0c4770241eae149b0d4cd8de329aee0 [1] upstream for the complete explanation.

[1] https://github.com/mesonbuild/meson/commit/3c7ab542c0c4770241eae149b0d4cd8de329aee0