add unit test for xor check

tests/2041-xor-checker/config.tcl

@@ -0,0 +1,2 @@
+set ::env(DESIGN_NAME) inverter
+

tests/2041-xor-checker/interactive.tcl

@@ -0,0 +1,6 @@
+package require openlane;
+
+prep -design $::env(TEST_DIR) {*}$argv
+
+set ::env(signoff_results) $::env(TEST_DIR)
+run_klayout_gds_xor

tests/2041-xor-checker/issue_regression.py

@@ -0,0 +1,21 @@
+import os
+import subprocess
+import sys
+
+args = sys.argv[1:]
+exit_code = args[1]
+run_folder = args[0]
+
+assert exit_code != 0, "OpenLane did not throw non zero exit code"
+log_path = os.path.join(run_folder, "openlane.log")
+assert (
+    subprocess.call(
+        [
+            "grep",
+            "-i",
+            "There are XOR differences in the design",
+            log_path,
+        ]
+    )
+    == 0
+), "OpenLane did not report the existence of XOR violations correctly"