ghc865-binary: Build with ncurses6. Fixes musl build error.

As proposed on NixOS#85924 (comment)

pkgs/development/compilers/ghc/8.6.5-binary.nix

@@ -1,6 +1,6 @@
 { stdenv
 , fetchurl, perl, gcc
-, ncurses5, gmp, glibc, libiconv
+, ncurses6, gmp, glibc, libiconv
 , llvmPackages
 }:
 
@@ -11,7 +11,7 @@ let
   useLLVM = !stdenv.targetPlatform.isx86;
 
   libPath = stdenv.lib.makeLibraryPath ([
-    ncurses5 gmp
+    ncurses6 gmp
   ] ++ stdenv.lib.optional (stdenv.hostPlatform.isDarwin) libiconv);
 
   libEnvVar = stdenv.lib.optionalString stdenv.hostPlatform.isDarwin "DY"
@@ -38,8 +38,12 @@ stdenv.mkDerivation rec {
       sha256 = "1p2h29qghql19ajk755xa0yxkn85slbds8m9n5196ris743vkp8w";
     };
     x86_64-linux = {
-      url = "http://haskell.org/ghc/dist/${version}/ghc-${version}-x86_64-deb9-linux.tar.xz";
-      sha256 = "1pqlx6rdjs2110g0y1i9f8x18lmdizibjqd15f5xahcz39hgaxdw";
+      # We use the `fedora27`-targeted bindist instead of the `deb9` one because
+      # it expects the `ncurses` ABI 6 instead of 5, as 5 made a problem, see:
+      # https://github.com/NixOS/nixpkgs/issues/85924#issuecomment-640277067
+      # TODO: Update the other `-linux` bindists accordingly and test them.
+      url = "http://haskell.org/ghc/dist/${version}/ghc-${version}-x86_64-fedora27-linux.tar.xz";
+      sha256 = "18dlqm5d028fqh6ghzn7pgjspr5smw030jjzl3kq6q1kmwzbay6g";
     };
     aarch64-linux = {
       url = "http://haskell.org/ghc/dist/${version}/ghc-${version}-aarch64-ubuntu18.04-linux.tar.xz";
@@ -90,7 +94,6 @@ stdenv.mkDerivation rec {
     stdenv.lib.optionalString stdenv.isLinux ''
       find . -type f -perm -0100 -exec patchelf \
           --replace-needed libncurses${stdenv.lib.optionalString stdenv.is64bit "w"}.so.5 libncurses.so \
-          --replace-needed libtinfo.so libtinfo.so.5 \
           --interpreter ${glibcDynLinker} {} \;
 
       sed -i "s|/usr/bin/perl|perl\x00        |" ghc-${version}/ghc/stage2/build/tmp/ghc-stage2