Install cmake/ninja in Linux test environment

The test phase runs in a fresh venv where the cmake/ninja installed
during BEFORE_ALL aren't available. Use CIBW_BEFORE_TEST_LINUX to
install them into the test venv.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: alexreinking

.github/workflows/pip.yml

@@ -138,6 +138,7 @@ jobs:
             CMAKE_GENERATOR=Ninja
             CMAKE_PREFIX_PATH='${{ github.workspace }}\opt'
             SETUPTOOLS_SCM_OVERRIDES_FOR_HALIDE='{local_scheme="no-local-version"}'
+          CIBW_BEFORE_TEST_LINUX: pip install cmake ninja
           CIBW_TEST_COMMAND: >
             cmake -G Ninja -S {project}/python_bindings/apps -B build -DCMAKE_BUILD_TYPE=Release &&
             cmake --build build &&