FILECHECKPATH -> FILECHECK and docs for setting this env var

Author: rolfmorel

.github/workflows/examples.yml

@@ -25,6 +25,5 @@ jobs:
 
       - name: Run lit-enabled examples as tests
         run: |
-          export FILECHECKPATH=FileCheck-18 # Ubuntu's llvm-dev appends a version number.
+          export FILECHECK=FileCheck-18 # Ubuntu's llvm-dev appends a version number.
           uv run lit python/examples  # Makes sure to substitute FileCheck for $FILECHECKPATH
-

README.md

@@ -123,4 +123,11 @@ pip install .[ingress_torch_cpu] \
 Running the tests is as simple as `lit .` in the root of the project.
 
 We assume that the [`FileCheck`](https://llvm.org/docs/CommandGuide/FileCheck.html) and [`lit`](https://llvm.org/docs/CommandGuide/lit.html) executables are available on the `PATH`.
+
+<details>
+<summary>
+Obtaining `FileCheck` and `lit`.
+</summary>
 To obtain the [Python package for `lit`](https://pypi.org/project/lit/), simply run `uv sync --group test`.
+In case the `FileCheck` executable happens to be available under a different name/location, e.g. as `FileCheck-18` from Ubuntu's `llvm-dev` package, set the `FILECHECK` environment variable when invoking `lit`.
+</details>

lit.cfg.py

@@ -12,5 +12,5 @@
 config.test_exec_root = os.path.dirname(__file__) + "/lit.out"
 
 config.substitutions.append(("%PYTHON", "uv run"))
-if filecheck_path := os.environ.get("FILECHECKPATH"):
+if filecheck_path := os.environ.get("FILECHECK"):
     config.substitutions.append(("FileCheck", filecheck_path))