Ignore and clean file .lia.cache

This file is created by Coq when running some tactics

Author: xavierleroy

.gitignore

@@ -67,4 +67,6 @@
 # MacOS metadata
 .DS_Store
 # Test generated data
-/test/clightgen/*.v
+/test/clightgen/*.v
+# Coq cache
+.lia.cache

Makefile

@@ -268,6 +268,7 @@ clean:
 	rm -f extraction/STAMP extraction/*.ml extraction/*.mli .depend.extr
 	rm -f tools/ndfun tools/modorder tools/*.cm? tools/*.o
 	rm -f $(GENERATED) .depend
+	rm -f .lia.cache
 	$(MAKE) -f Makefile.extr clean
 	$(MAKE) -C runtime clean
 	$(MAKE) -C test clean