package/nginx: fix build failure

Correctly set NGX_SYS_NERR, even when it is 0.

Fixes:
  http://autobuild.buildroot.org/results/666/666d780bf61e10c9f89f765bb04ddc1afc11d0d1/
  http://autobuild.buildroot.org/?reason=nginx-1.6.2&&arch=powerpc

Signed-off-by: Samuel Martin <s.martin49@gmail.com>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>

package/nginx/nginx-0005-auto-unix-make-sys_nerr-guessing-cross-friendly.patch

@@ -22,7 +22,7 @@ new file mode 100644
 index 0000000..25e7c22
 --- /dev/null
 +++ b/auto/os/sys_nerr
-@@ -0,0 +1,77 @@
+@@ -0,0 +1,78 @@
 +
 +# Copyright (C) Samuel Martin <s.martin49@gmail.com>
 +
@@ -89,6 +89,7 @@ index 0000000..25e7c22
 +
 +if test -z $ngx_sys_nerr ; then
 +    ngx_size=0
++    ngx_sys_nerr=0
 +fi
 +
 +cat << END >> $NGX_AUTO_CONFIG_H