Prevent check-local-headers.sh hang.

Consensus in [1] was that the right way to fix this was simply to
redirect from /dev/null to terminate the test if no inputs was found
by the tests own globbing e.g. "*/*.{o,os,oS}.d" This can happen when
the build is incomplete and the tests are started. This failure causes
check-local-headers.sh to hang forever waiting for input from stdin.
This change makes the test terminate immediately if the glob doesn't
return any files.

[1] https://sourceware.org/ml/libc-alpha/2014-12/msg00337.html

ChangeLog

@@ -1,3 +1,8 @@
+2015-09-14  Carlos O'Donell  <carlos@redhat.com>
+
+	* Makefile ($(objpfx)check-local-headers.out): Redirect stdin from
+	/dev/null.
+
 2015-09-13  Samuel Thibault  <samuel.thibault@ens-lyon.org>
 
 	* sysdeps/mach/hurd/Makefile ($(patsubst %,$(hurd-objpfx)hurd/%.%,auth

Makefile

@@ -262,7 +262,7 @@ endif
 
 $(objpfx)check-local-headers.out: scripts/check-local-headers.sh
 	AWK='$(AWK)' scripts/check-local-headers.sh \
-	  "$(includedir)" "$(objpfx)" > $@; \
+	  "$(includedir)" "$(objpfx)" < /dev/null > $@; \
 	$(evaluate-test)
 
 ifneq ($(PERL),no)