Also use the C locale for re-checking our list of tests

otherwise, when the tests directory contains vtc files whose names
get sorted differently in the current environment's locale than in C,
config.status will get re-run for every make check invocation, which
is particularly annoying with parallel makes

bin/varnishtest/Makefile.am

@@ -9,6 +9,7 @@ check: check-am check-local
 check-am: check-local
 # See if list of checks have changed, recheck
 check-local:
+	LC_ALL=C; \
 	if [ "$$(cd $(srcdir) && echo tests/*.vtc)" != "@VTC_TESTS@" ]; then \
 		cd $(top_builddir) && ./config.status --recheck ; \
 	fi