Issue #7386: fix languages non-provided by InnoSetup showing as English.

The language files provided by the InnoSetup project (either the main
ones or the "Unofficial" ones, i.e. less maintained ones) at least
provides the name of the language, possibly in English, ideally
self-localized in its own language.

Unfortunately Kabyle didn't have any language file so we were using the
Default one, which ended up showing the lang as a duplicate (and very
wrong) "English".

With this commit, I add code to provide our own very basic base language
file, which would at least contain the language name. There is also a
concept of language ID to be verified in Windows-provided list.
Unfortunately it doesn't have any (actually it was id-ed 0x1000 like
many other languages, which looked therefore to be the code for an
unsupported lang). InnoSetup docs tells us to leave 0 then. We can add
the ability to set a specific code later in the template if we add other
un-provided languages and if they have their own lang id.

With this base infrastructure, we should be able to better support more
languages.

build/windows/installer/gimp3264.iss

@@ -207,7 +207,7 @@ Name: "is"; MessagesFile: "compiler:Languages\Icelandic.isl,lang\is.setup.isl"
 Name: "it"; MessagesFile: "compiler:Languages\Italian.isl,lang\it.setup.isl"
 Name: "ja"; MessagesFile: "compiler:Languages\Japanese.isl,lang\ja.setup.isl"
 Name: "ka"; MessagesFile: "compiler:Languages\Unofficial\Georgian.isl,lang\ka.setup.isl"
-Name: "kab"; MessagesFile: "compiler:Default.isl,lang\kab.setup.isl"
+Name: "kab"; MessagesFile: "compiler:Default.isl,lang\kab.isl,lang\kab.setup.isl"
 Name: "ko"; MessagesFile: "compiler:Languages\Unofficial\Korean.isl,lang\ko.setup.isl"
 Name: "lt"; MessagesFile: "compiler:Languages\Unofficial\Lithuanian.isl,lang\lt.setup.isl"
 Name: "lv"; MessagesFile: "compiler:Languages\Unofficial\Latvian.isl,lang\lv.setup.isl"

build/windows/installer/lang/meson.build

@@ -28,7 +28,7 @@ languages = [
   { 'code': 'it',    },
   { 'code': 'ja',    },
   { 'code': 'ka',    },
-  { 'code': 'kab',   },
+  { 'code': 'kab',   'langname': 'Taqbaylit' },
   { 'code': 'ko',    },
   { 'code': 'lt',    },
   { 'code': 'lv',    },
@@ -105,6 +105,21 @@ foreach language : languages
     ],
     build_by_default: true,
   )
+
+  if 'langname' in language
+    # Some languages may have no default language file provided by
+    # InnoSetup. When this happens, we must at least complete a very
+    # basic file showing the language name, otherwise it shows as
+    # "English".
+    newlang_isl = '@0@.isl'.format(language.get('code'))
+    newlang_conf = configuration_data()
+    newlang_conf.set('LANGNAME', language.get('langname'))
+    configure_file(
+      input : 'newlang.isl.in',
+      output : newlang_isl,
+      configuration : newlang_conf
+    )
+  endif
 endforeach
 
 test('windows-installer-langs',

build/windows/installer/lang/newlang.isl.in

@@ -0,0 +1,15 @@
+; A template to create the basic lang file for languages which are not
+; made available by InnoSetup, not even in the Unofficial/ folder.
+; See full list of languages:
+; https://github.com/jrsoftware/issrc/tree/main/Files/Languages
+;
+; Without this, they show as English in the
+; start list so we must add a language name (localized preferably) at
+; the very least.
+; See also the docs for the meanings of different fields:
+; https://jrsoftware.org/ishelp/index.php?topic=langoptionssection
+
+[LangOptions]
+LanguageName=@LANGNAME@
+LanguageID=$0
+LanguageCodePage=0