haskellPackages.mkDerivation: get ghclibdir via haskellCompilerName

This is the correctest and clearest way to do it I can think of at the
moment that doesn't need us to add anything.
"${ghcCommand}-${ghc.version}" also works, but is clunkier and harder to
replicate for downstream users.

pkgs/development/haskell-modules/generic-builder.nix

@@ -195,13 +195,13 @@ let
     "--prefix=$out"
     "--libdir=\\$prefix/lib/\\$compiler"
     "--libsubdir=\\$abi/\\$libname"
-    (optionalString enableSeparateDataOutput "--datadir=$data/share/${ghc.name}")
+    (optionalString enableSeparateDataOutput "--datadir=$data/share/${ghcNameWithPrefix}")
     (optionalString enableSeparateDocOutput "--docdir=${docdir "$doc"}")
   ] ++ optionals stdenv.hasCC [
     "--with-gcc=$CC" # Clang won't work without that extra information.
   ] ++ [
     "--package-db=$packageConfDir"
-    (optionalString (enableSharedExecutables && stdenv.isLinux) "--ghc-option=-optl=-Wl,-rpath=$out/lib/${ghc.name}/${pname}-${version}")
+    (optionalString (enableSharedExecutables && stdenv.isLinux) "--ghc-option=-optl=-Wl,-rpath=$out/lib/${ghcNameWithPrefix}/${pname}-${version}")
     (optionalString (enableSharedExecutables && stdenv.isDarwin) "--ghc-option=-optl=-Wl,-headerpad_max_install_names")
     (optionalString enableParallelBuilding "--ghc-options=${parallelBuildingFlags}")
     (optionalString useCpphs "--with-cpphs=${cpphs}/bin/cpphs --ghc-options=-cpp --ghc-options=-pgmP${cpphs}/bin/cpphs --ghc-options=-optP--cpp")
@@ -274,6 +274,8 @@ let
   ghcCommand' = if isGhcjs then "ghcjs" else "ghc";
   ghcCommand = "${ghc.targetPrefix}${ghcCommand'}";
 
+  ghcNameWithPrefix = "${ghc.targetPrefix}${ghc.haskellCompilerName}";
+
   nativeGhcCommand = "${nativeGhc.targetPrefix}ghc";
 
   buildPkgDb = ghcName: packageConfDir: ''
@@ -349,14 +351,14 @@ stdenv.mkDerivation ({
   # pkgs* arrays defined in stdenv/setup.hs
   + ''
     for p in "''${pkgsBuildBuild[@]}" "''${pkgsBuildHost[@]}" "''${pkgsBuildTarget[@]}"; do
-      ${buildPkgDb nativeGhc.name "$setupPackageConfDir"}
+      ${buildPkgDb "${nativeGhcCommand}-${nativeGhc.version}" "$setupPackageConfDir"}
     done
     ${nativeGhcCommand}-pkg --${nativePackageDbFlag}="$setupPackageConfDir" recache
   ''
   # For normal components
   + ''
     for p in "''${pkgsHostHost[@]}" "''${pkgsHostTarget[@]}"; do
-      ${buildPkgDb ghc.name "$packageConfDir"}
+      ${buildPkgDb ghcNameWithPrefix "$packageConfDir"}
       if [ -d "$p/include" ]; then
         configureFlags+=" --extra-include-dirs=$p/include"
       fi
@@ -493,7 +495,7 @@ stdenv.mkDerivation ({
       # just the target specified; "install" will error here, since not all targets have been built.
     else ''
       ${setupCommand} copy ${buildTarget}
-      local packageConfDir="$out/lib/${ghc.name}/package.conf.d"
+      local packageConfDir="$out/lib/${ghcNameWithPrefix}/package.conf.d"
       local packageConfFile="$packageConfDir/${pname}-${version}.conf"
       mkdir -p "$packageConfDir"
       ${setupCommand} register --gen-pkg-config=$packageConfFile