[GLib][Ruby] undefined method 'compute_initialize' for module Arrow (NoMethodError)

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

Raise the exception below when `ARROW_COMPUTE` OFF

```
( cd c_glib ; ../c_glib/test/run-test.sh )
/path/to/arrow/c_glib/test/run-test.rb:34:in '': undefined method 'compute_initialize' for module Arrow (NoMethodError)

Arrow.compute_initialize
^^^^^^^^^^^^^^^^^^^
```

## Reproduce steps

```
git clone https://github.com/apache/arrow/
cd arrow/cpp
mkdir build
cd build
cmake .. --preset ninja-debug-maximal \
-DCMAKE_INSTALL_PREFIX=/tmp/local \
-DARROW_CUDA=OFF \
-DARROW_SKYHOOK=OFF \
-DCMAKE_OSX_SYSROOT=/Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX.sdk \
-DARROW_EXTRA_ERROR_CONTEXT=OFF
cmake --build .
cmake --install .
```

```
meson setup \
--backend=ninja \
--prefix=/tmp/local \
--libdir=lib \
--pkg-config-path=/tmp/local/lib/pkgconfig \
-Ddoc=false \
-Dvapi=false \
-Dwerror=false \
c_glib.build \
c_glib
ninja -C c_glib.build all
```

## Environment

* macOS: 15.5
* Apache Arrow: 5f0aeb5de53fb25b59a52661a80071faef99a4a4

### Component(s)

GLib