gnused: Fix cross build after upgrade to 4.3.0

Fixes:
````
  GEN      doc/sed.1
help2man: can't get `--help' info from sed/sed
make[2]: *** [Makefile:5775: doc/sed.1] Error 126
make[2]: Leaving directory '/tmp/nix-build-gnused-4.3-arm-linux-gnueabihf.drv-0/sed-4.3'
make[1]: *** [Makefile:3024: all-recursive] Error 1
make[1]: Leaving directory '/tmp/nix-build-gnused-4.3-arm-linux-gnueabihf.drv-0/sed-4.3'
make: *** [Makefile:2156: all] Error 2
````

http://hydra.nixos.org/build/46051086/nixlog/11/raw

1 files changed, 8 insertions, 0 deletions

diff --git a/pkgs/tools/text/gnused/default.nix b/pkgs/tools/text/gnused/default.nix
index aa25101636e..ca038b3ccb4 100644
--- a/pkgs/tools/text/gnused/default.nix
+++ b/pkgs/tools/text/gnused/default.nix
@@ -14,6 +14,14 @@ stdenv.mkDerivation rec {
   nativeBuildInputs = [ perl ];
   preConfigure = "patchShebangs ./build-aux/help2man";
 
+  crossAttrs = {
+    # The tarball ships with a fine prebuilt manpage, but the make rules try to rebuild it,
+    # which won't work when cross compiling as help2man needs to execute the binaries.
+    postConfigure = ''
+      sed -i Makefile -e 's|doc/sed\.1:|dummy:|'
+    '';
+  };
+
   meta = {
     homepage = http://www.gnu.org/software/sed/;
     description = "GNU sed, a batch stream editor";