maint: ignore 'make syntax-check' failure files

* .gitignore: Add exemption.
* cfg.mk (local-checks-to-skip): Ignore a test to silence a skip
warning.

.gitignore

@@ -7,6 +7,7 @@
 *~
 .git
 .git-module-status
+.sc-start-sc_*
 /GNUmakefile
 /maint.mk
 ABOUT-NLS

cfg.mk

@@ -34,6 +34,7 @@ local-checks-to-skip =			\
   sc_GPL_version			\
   sc_always_defined_macros		\
   sc_cast_of_alloca_return_value	\
+  sc_cross_check_PATH_usage_in_tests	\
   sc_dd_max_sym_length			\
   sc_error_exit_success			\
   sc_file_system			\