Merge pull request #3976 from Pinata-Consulting/lec-optinal

flow: only enable LEC_CHECK when kepler-formal is installed

Author: maliberty

flow/settings.mk

@@ -1 +1,5 @@
-export LEC_CHECK ?= 1
+# Enable LEC (Logical Equivalence Check) only if kepler-formal is installed.
+# kepler-formal is primarily an OpenROAD/ORFS developer tool, not an end-user
+# tool. End-users would typically run LEC transactionally at project completion,
+# not in every CI run where it wastes CI time.
+export LEC_CHECK ?= $(if $(wildcard $(KEPLER_FORMAL_EXE)),1,0)