maint: tweak sc_check-I18N-AUTHORS

* cfg.mk (sc_check-I18N-AUTHORS): Remove unnecessary subshell;
add a self-explanatory diagnostic.

cfg.mk

@@ -181,13 +181,15 @@ sc_check-AUTHORS: $(all_programs)
 	  && diff $(au_actual) $(au_dotdot) \
 	  && rm -f $(au_actual) $(au_dotdot)
 
-# Ensure programs with authors with non ASCII names link with LIBICONV
+# Each program with a non-ASCII author name must link with LIBICONV.
 sc_check-I18N-AUTHORS:
-	@(cd $(srcdir)/src &&                           \
+	@cd $(srcdir)/src &&						\
 	  for i in $$(git grep -l -w proper_name_utf8 *.c|sed 's/\.c//'); do \
-	    grep -E "^src_$${i}_LDADD"' .?= .*\$$\(LIBICONV\)' local.mk > \
-	      /dev/null || { echo FAIL $$i; exit 1; };            \
-	  done)
+	    grep -E "^src_$${i}_LDADD"' .?= .*\$$\(LIBICONV\)' local.mk	\
+		> /dev/null						\
+	      || { "echo $(ME): link rules for $$i do not include"	\
+		    '$$(LIBICONV)' 1>&2; exit 1; };			\
+	  done
 
 # Look for lines longer than 80 characters, except omit:
 # - program-generated long lines in diff headers,