app/build.gradle

@@ -585,16 +585,22 @@ task buildTranslationArray {
     // This isn't running as a task, instead the array is build when the gradle file is parsed.
     // https://github.com/mozilla-mobile/fenix/issues/14175
     def foundLocales = new StringBuilder()
+    def languageCodes = []
     foundLocales.append("new String[]{")
 
     fileTree("src/main/res").visit { FileVisitDetails details ->
         if(details.file.path.endsWith("/strings.xml")){
             def languageCode = details.file.parent.tokenize('/').last().replaceAll('values-','').replaceAll('-r','-')
             languageCode = (languageCode == "values") ? "en-US" : languageCode
-            foundLocales.append("\"").append(languageCode).append("\"").append(",")
+            languageCodes.add(languageCode)
         }
     }
-
+    // The order of files in a `FileTree` is not stable, even on a single
+    // computer. Thus we need to sort the `languageCode`s. See: fenix#40083.
+    languageCodes.sort()
+    languageCodes.each {
+        foundLocales.append("\"").append(it).append("\"").append(",")
+    }
     foundLocales.append("}")
     def foundLocalesString = foundLocales.toString().replaceAll(',}','}')
     android.defaultConfig.buildConfigField "String[]", "SUPPORTED_LOCALE_ARRAY", foundLocalesString