Use Il2CppCodeGeneration.OptimizeSpeed in Android and iOS release exports.

Author: timbotimbo

example/unity/DemoApp/Assets/FlutterUnityIntegration/Editor/Build.cs

@@ -3,6 +3,7 @@
 using System.Linq;
 using System.Text.RegularExpressions;
 using UnityEditor;
+using UnityEditor.Build;
 using UnityEngine;
 using Application = UnityEngine.Application;
 using BuildResult = UnityEditor.Build.Reporting.BuildResult;
@@ -211,10 +212,10 @@ private static void DoBuildAndroid(String buildPath, bool isPlugin, bool isRelea
             }
             #if UNITY_2022_1_OR_NEWER
                 PlayerSettings.SetIl2CppCompilerConfiguration(BuildTargetGroup.Android, isReleaseBuild ? Il2CppCompilerConfiguration.Release : Il2CppCompilerConfiguration.Debug);
-                PlayerSettings.SetIl2CppCodeGeneration(UnityEditor.Build.NamedBuildTarget.Android, UnityEditor.Build.Il2CppCodeGeneration.OptimizeSize);
+                PlayerSettings.SetIl2CppCodeGeneration(NamedBuildTarget.Android, isReleaseBuild ? Il2CppCodeGeneration.OptimizeSpeed : Il2CppCodeGeneration.OptimizeSize);
             #elif UNITY_2021_2_OR_NEWER
                 PlayerSettings.SetIl2CppCompilerConfiguration(BuildTargetGroup.Android, isReleaseBuild ? Il2CppCompilerConfiguration.Release : Il2CppCompilerConfiguration.Debug);
-                EditorUserBuildSettings.il2CppCodeGeneration = UnityEditor.Build.Il2CppCodeGeneration.OptimizeSize;
+                EditorUserBuildSettings.il2CppCodeGeneration = isReleaseBuild ? Il2CppCodeGeneration.OptimizeSpeed : Il2CppCodeGeneration.OptimizeSize;
             #endif
 
             // Switch to Android standalone build.
@@ -416,10 +417,10 @@ private static void BuildIOS(String path, bool isReleaseBuild)
 
             #if UNITY_2022_1_OR_NEWER
                 PlayerSettings.SetIl2CppCompilerConfiguration(BuildTargetGroup.iOS, isReleaseBuild ? Il2CppCompilerConfiguration.Release : Il2CppCompilerConfiguration.Debug);
-                PlayerSettings.SetIl2CppCodeGeneration(UnityEditor.Build.NamedBuildTarget.iOS, UnityEditor.Build.Il2CppCodeGeneration.OptimizeSize);
+                PlayerSettings.SetIl2CppCodeGeneration(NamedBuildTarget.iOS, isReleaseBuild ? Il2CppCodeGeneration.OptimizeSpeed : Il2CppCodeGeneration.OptimizeSize);
             #elif UNITY_2021_2_OR_NEWER
                 PlayerSettings.SetIl2CppCompilerConfiguration(BuildTargetGroup.iOS, isReleaseBuild ? Il2CppCompilerConfiguration.Release : Il2CppCompilerConfiguration.Debug);
-                EditorUserBuildSettings.il2CppCodeGeneration = UnityEditor.Build.Il2CppCodeGeneration.OptimizeSize;
+                EditorUserBuildSettings.il2CppCodeGeneration = isReleaseBuild ? Il2CppCodeGeneration.OptimizeSpeed : Il2CppCodeGeneration.OptimizeSize;
             #endif
 
             var playerOptions = new BuildPlayerOptions