tests: prohibit fail=0 initialization

* cfg.mk (sc_prohibit_fail_0): New rule.
* .x-sc_prohibit_fail_0: New file.
* Makefile.am (syntax_check_exceptions): Distribute the new file.

.x-sc_prohibit_fail_0

@@ -0,0 +1,3 @@
+\.mk$
+/Makefile\.am$
+^tests/test-lib\.sh$

Makefile.am

@@ -47,6 +47,7 @@ syntax_check_exceptions =		\
   .x-sc_po_check			\
   .x-sc_program_name			\
   .x-sc_prohibit_atoi_atof		\
+  .x-sc_prohibit_fail_0			\
   .x-sc_prohibit_magic_number_exit	\
   .x-sc_prohibit_stat_st_blocks		\
   .x-sc_prohibit_strcmp			\

cfg.mk

@@ -232,13 +232,9 @@ sc_prohibit_emacs__indent_tabs_mode__setting:
 
 # Ensure that each file that contains fail=1 also contains fail=0.
 # Otherwise, setting file=1 in the environment would make tests fail unexpectedly.
-sc_fail_is_initialized:
-	@files=$$(grep -l -E '\<fail=1$$' $$($(VC_LIST_EXCEPT)));	\
-	if test "$$?" = 0; then						\
-	  grep -LE '\<fail=0$$' $$files | grep . &&			\
-	    { echo '$(ME): the above files do not set fail=0'		\
-		1>&2; exit 1; } || :;					\
-	else :;								\
-	fi
+sc_prohibit_fail_0:
+	@re='\<fail=0\>'						\
+	msg='fail=0 initialization'					\
+	  $(_prohibit_regexp)
 
 include $(srcdir)/dist-check.mk