psmisc: fix cross-compiling

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

···
   nativeBuildInputs = [ autoconf automake gettext ];
   buildInputs = [ ncurses ];
 
-  preConfigure = ''
+  preConfigure = stdenv.lib.optionalString (stdenv.buildPlatform != stdenv.hostPlatform) ''
+    # Goes past the rpl_malloc linking failure
+    export ac_cv_func_malloc_0_nonnull=yes
+    export ac_cv_func_realloc_0_nonnull=yes
+  '' + ''
     echo $version > .tarball-version
     ./autogen.sh
   '';