Fix wvdial build by inserting missing unistd.h includes

pkgs/development/libraries/wvstreams/default.nix

@@ -12,6 +12,8 @@ stdenv.mkDerivation {
 
   preConfigure = ''
     find -type f | xargs sed -i 's@/bin/bash@bash@g'
+
+    sed -e '1i#include <unistd.h>' -i $(find . -name '*.c' -o -name '*.cc')
   '';
 
   buildInputs = [ qt4 dbus zlib openssl readline perl ];

pkgs/os-specific/linux/wvdial/default.nix

@@ -15,6 +15,8 @@ stdenv.mkDerivation rec {
     export makeFlags="prefix=$out"
     # not sure about this line
     sed -i 's@/etc/ppp/peers@$out/etc/ppp/peers@' Makefile.in
+
+    sed -e '1i#include <unistd.h>' -i $(find . -name '*.cc')
   '';
 
   meta = {