btar: fix build by reintroducing librsync 0.9.x for ZHF

pkgs/development/libraries/librsync/0.9.nix

@@ -0,0 +1,22 @@
+{stdenv, fetchurl}:
+
+stdenv.mkDerivation {
+  name = "librsync-0.9.7";
+  
+  src = fetchurl {
+    url = mirror://sourceforge/librsync/librsync-0.9.7.tar.gz;
+    sha256 = "1mj1pj99mgf1a59q9f2mxjli2fzxpnf55233pc1klxk2arhf8cv6";
+  };
+
+  configureFlags = if stdenv.isCygwin then "--enable-static" else "--enable-shared";
+
+  crossAttrs = {
+    dontStrip = true;
+  };
+
+  meta = {
+    homepage = http://librsync.sourceforge.net/;
+    license = stdenv.lib.licenses.lgpl2Plus;
+    description = "Implementation of the rsync remote-delta algorithm";
+  };
+}

pkgs/top-level/all-packages.nix

@@ -891,7 +891,9 @@ let
 
   bsdiff = callPackage ../tools/compression/bsdiff { };
 
-  btar = callPackage ../tools/backup/btar { };
+  btar = callPackage ../tools/backup/btar {
+    librsync = librsync_0_9;
+  };
 
   bud = callPackage ../tools/networking/bud {
     inherit (pythonPackages) gyp;
@@ -6744,6 +6746,8 @@ let
 
   librsync = callPackage ../development/libraries/librsync { };
 
+  librsync_0_9 = callPackage ../development/libraries/librsync/0.9.nix { };
+
   libsearpc = callPackage ../development/libraries/libsearpc { };
 
   libsigcxx = callPackage ../development/libraries/libsigcxx { };