ci(tool): Use llvm-lit for running translator tests

Previously testing the translator relied on cmake, but this causes issues when the build stage runs on a different runner to the test stage, since cmake encodes absolute paths to the tools it uses.

This commit relies instead on the llvm-lit tool that the cmake target is designed to invoke.

One side effect of this change is that the test surface of the translator is reduced, since we no longer invoke cmake --build . --target check-mlir-serialize-deserialize, which is part of the docs in mlir_translator/README.md.

Signed-off-by: Luke Hutton luke.hutton@arm.com