bc: fixes for cross-compilation

pkgs/tools/misc/bc/default.nix

@@ -1,4 +1,4 @@
-{stdenv, fetchurl, flex, readline, ed, texinfo}:
+{stdenv, autoreconfHook, buildPackages, fetchurl, flex, readline, ed, texinfo}:
 
 stdenv.mkDerivation rec {
   name = "bc-1.07.1";
@@ -9,9 +9,24 @@ stdenv.mkDerivation rec {
 
   configureFlags = [ "--with-readline" ];
 
-  buildInputs = [flex readline ed texinfo];
+  # As of 1.07 cross-compilation is quite complicated as the build system wants
+  # to build a code generator, bc/fbc, on the build machine.
+  patches = [ ./cross-bc.patch ];
+  depsBuildBuild = [ buildPackages.stdenv.cc ];
+  nativeBuildInputs = [
+    # Tools
+    autoreconfHook ed flex texinfo
+    # Libraries for build
+    buildPackages.readline buildPackages.ncurses
+  ];
+  buildInputs = [ readline ];
 
-  doCheck = true;
+  doCheck = true; # not cross
+
+  # Hack to make sure we never to the relaxation `$PATH` and hooks support for
+  # compatability. This will be replaced with something clearer in a future
+  # masss-rebuild.
+  crossConfig = true;
 
   meta = {
     description = "GNU software calculator";