package/nginx-naxsi: add missing pcre dependency

Fixes:
  http://autobuild.buildroot.net/results/9c7/9c7bad6831b09251af81e2bbfc595a241df87c70/

Signed-off-by: Samuel Martin <s.martin49@gmail.com>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>

package/nginx-naxsi/Config.in

@@ -1,5 +1,6 @@
 config BR2_PACKAGE_NGINX_NAXSI
 	bool "nginx-naxsi"
+	select BR2_PACKAGE_PCRE
 	help
 	  NAXSI means Nginx Anti XSS & SQL Injection.