djbdns: fix build in usernamespaces

pkgs/tools/networking/djbdns/default.nix

@@ -18,7 +18,7 @@ stdenv.mkDerivation {
     sha256 = "0j3baf92vkczr5fxww7rp1b7gmczxmmgrqc8w2dy7kgk09m85k9w";
   };
 
-  patches = [ ./hier.patch ];
+  patches = [ ./hier.patch ./fix-nix-usernamespace-build.patch ];
 
   postPatch = ''
     echo gcc -O2 -include ${glibc.dev}/include/errno.h > conf-cc
@@ -45,4 +45,4 @@ stdenv.mkDerivation {
     license = licenses.publicDomain;
     maintainers = with maintainers; [ jerith666 ];
   };
-}
+}

pkgs/tools/networking/djbdns/fix-nix-usernamespace-build.patch

@@ -0,0 +1,10 @@
+--- djbdns-1.05.org/chkshsgr.c	2001-02-11 21:11:45.000000000 +0000
++++ djbdns-1.05/chkshsgr.c	2017-10-13 10:06:09.392578927 +0100
+@@ -2,6 +2,7 @@
+ 
+ int main()
+ {
++  return 0;
+   short x[4];
+ 
+   x[0] = x[1] = 0;