i18n: repair language names for Chinese

Prompted by Linlinger, I've reconsidered the names of languages
in the drop-down in the welcome page. We already have the
infrastructure for assigning specific names / locales to
"Calamares locale names" (which match Transifex names, not
necessarily Qt names). Use that to put exactly two Chinese-
language translations in the drop-down:
- Simplified Chinese (code zh_CN)
- Traditional Chinese (code zh_TW)
Drop zh (which is a peculiar locale name anyway) and zh_HK
(which is Traditional Chinese, but using the geographic
boundary is a bit weird; we're going to ignore the
minor orthographic differences with Traditional Chinese
written elsewhere for now).

Note that this makes the drop-down show "Chinese"
in the English column, twice; the difference is visible
only in the native-language representation.

SEE #1741

CMakeLists.txt

@@ -138,9 +138,9 @@ set( _tx_complete az az_AZ ca de fi_FI he hi hr ja ko lt pt_BR sq
 set( _tx_good as be ca@valencia cs_CZ da fr fur it_IT ml nl pt_PT
     ru sk tg tr_TR vi zh_CN )
 set( _tx_ok ar ast bg bn el en_GB es es_MX es_PR et eu fa gl hu id
-    is mr nb pl ro si sl sr sr@latin th zh_HK )
+    is mr nb pl ro si sl sr sr@latin th )
 set( _tx_incomplete eo es_PE fr_CH gu id_ID ie kk kn ko_KR lo lv mk
-    ne ne_NP ru_RU te ur uz zh )
+    ne ne_NP ru_RU te ur uz )
 
 ### Required versions
 #

src/libcalamares/locale/Translation.cpp

@@ -38,6 +38,18 @@ specialCase( const CalamaresUtils::Locale::Translation::Id& locale )
         static QString name = QStringLiteral( "Català (València)" );
         return { nullptr, &name };
     }
+    if ( localeName == "zh_CN" )
+    {
+        // Simplified Chinese, but drop the (China) from the name
+        static QString name = QStringLiteral( "简体中文" );
+        return { nullptr, &name };
+    }
+    if ( localeName == "zh_TW" )
+    {
+        // Traditional Chinese, but drop (Taiwan) from the name
+        static QString name = QStringLiteral( "繁體中文" );
+        return { nullptr, &name };
+    }
 
     return { nullptr, nullptr };
 }
@@ -70,11 +82,9 @@ Translation::Translation( const Id& localeId, LabelFormat format, QObject* paren
     }
 
     bool needsCountryName = ( format == LabelFormat::AlwaysWithCountry )
-        || ( localeId.name.contains( '_' ) && QLocale::countriesForLanguage( m_locale.language() ).count() > 1 );
+        || ( !name && localeId.name.contains( '_' )
-    QString countryName = ( needsCountryName ?
+             && QLocale::countriesForLanguage( m_locale.language() ).count() > 1 );
-
+    QString countryName = needsCountryName ? m_locale.nativeCountryName() : QString();
-                                             m_locale.nativeCountryName()
-                                             : QString() );
     m_label = needsCountryName ? longFormat.arg( languageName, countryName ) : languageName;
     m_englishLabel = needsCountryName ? longFormat.arg( englishName, QLocale::countryToString( m_locale.country() ) )
                                       : englishName;