build-unit-test-docker: Use `meson setup`

Invoking meson with only a build directory argument is deprecated:

```
2 10:14:32 andrew@fedora:~$ meson --version
1.1.0
2 10:17:32 andrew@fedora:~$ meson builddir
...
WARNING: Running the setup command as `meson [options]` instead of `meson setup [options]` is ambiguous and deprecated.
2 10:17:34 andrew@fedora:~$
```

Change-Id: I29c087cce5b4c2bc928a1cd4c6f2c0afa74a447f
Signed-off-by: Andrew Jeffery <andrew@aj.id.au>
diff --git a/scripts/build-unit-test-docker b/scripts/build-unit-test-docker
index 93506e9..ec51c92 100755
--- a/scripts/build-unit-test-docker
+++ b/scripts/build-unit-test-docker
@@ -562,7 +562,7 @@
     def _cmd_build_meson(self) -> str:
         options = " ".join(self.pkg_def.get("config_flags", []))
         env = " ".join(self.pkg_def.get("config_env", []))
-        result = f"{env} meson builddir {meson_flags} {options} && "
+        result = f"{env} meson setup builddir {meson_flags} {options} && "
         result += "ninja -C builddir && ninja -C builddir install"
         return result