Support ruff discovery in pip build environments

Signed-off-by: Bernát Gábor <bgabor8@bloomberg.net>

python/ruff/__main__.py

@@ -33,6 +33,24 @@ def find_ruff_bin() -> str:
     if os.path.isfile(target_path):
         return target_path
 
+    # Might be a pip build environment
+    paths = os.environ.get("PATH", "").split(os.pathsep)
+    if len(paths) >= 2:
+        # https://github.com/pypa/pip/blob/main/src/pip/_internal/build_env.py#L87
+        first, second = os.path.split(paths[0]), os.path.split(paths[1])
+        # we need an overlay and normal folder within pip-build-env-{random} folders
+        if (
+            len(first) >= 3
+            and len(second) >= 3
+            and first[-3].startswith("pip-build-env-")
+            and first[-2] == "overlay"
+            and second[-3].startswith("pip-build-env-")
+            and second[-2] == "normal"
+        ):
+            candidate = os.path.join(first, ruff_exe) # the overlay contains ruff
+            if os.path.isfile(candidate):
+                return candidate
+
     raise FileNotFoundError(scripts_path)