hunspellDicts.fr-any: link fr-moderne to fr_FR

Some packages like `ibus-engines.typing-booster` require the dictionary
`fr_FR.dic` to provide proper support for the french language.

Until now the hunspell package set of nixpkgs didn't provide this
dictionary. It has been recommended to use `fr-moderne` as base and link
`fr_FR.dic` from it as done by other distros such as ArchLinux.

See https://github.com/NixOS/nixpkgs/issues/46940#issuecomment-423684570

Fixes #46940

nixos/doc/manual/release-notes/rl-1909.xml

@@ -156,6 +156,12 @@
      </listitem>
     </itemizedlist>
    </listitem>
+   <listitem>
+    <para>
+      The <literal>hunspellDicts.fr-any</literal> dictionary now ships with <literal>fr_FR.{aff,dic}</literal>
+      which is linked to <literal>fr-toutesvariantes.{aff,dic}</literal>.
+    </para>
+   </listitem>
   </itemizedlist>
  </section>
 </section>

pkgs/development/libraries/hunspell/dictionaries.nix

@@ -20,6 +20,7 @@ let
       # docs
       install -dm755 "$out/share/doc"
       install -m644 ${readmeFile} $out/share/doc/${name}.txt
+      runHook postInstall
     '';
   } // args);
 
@@ -107,7 +108,7 @@ let
     };
 
   mkDictFromDicollecte =
-    { shortName, shortDescription, longDescription, dictFileName }:
+    { shortName, shortDescription, longDescription, dictFileName, isDefault ? false }:
     mkDict rec {
       inherit dictFileName;
       version = "5.3";
@@ -131,6 +132,12 @@ let
       unpackCmd = ''
         unzip $src ${dictFileName}.dic ${dictFileName}.aff ${readmeFile}
       '';
+      postInstall = stdenv.lib.optionalString isDefault ''
+        for ext in aff dic; do
+          ln -sv $out/share/hunspell/${dictFileName}.$ext $out/share/hunspell/fr_FR.$ext
+          ln -sv $out/share/myspell/dicts/${dictFileName}.$ext $out/share/myspell/dicts/fr_FR.$ext
+        done
+      '';
     };
 
   mkDictFromWordlist =
@@ -483,6 +490,7 @@ in {
       réformées, suivant la lente évolution de l’orthographe actuelle. Ce
       dictionnaire contient les graphies les moins polémiques de la réforme.
     '';
+    isDefault = true;
   };
 
   fr-reforme1990 = mkDictFromDicollecte {