Add compile flag for whole program optimization

Source/Tools/Flax.Build/Build/NativeCpp/CompileEnvironment.cs

@@ -56,6 +56,11 @@ namespace Flax.Build.NativeCpp
         /// </summary>
         public bool Optimization = false;
 
+        /// <summary>
+        /// Enables the whole program optimization.
+        /// </summary>
+        public bool WholeProgramOptimization = false;
+
         /// <summary>
         /// Enables functions level linking support.
         /// </summary>
@@ -131,6 +136,7 @@ namespace Flax.Build.NativeCpp
                 RuntimeTypeInfo = RuntimeTypeInfo,
                 Inlining = Inlining,
                 Optimization = Optimization,
+                WholeProgramOptimization = WholeProgramOptimization,
                 FunctionLevelLinking = FunctionLevelLinking,
                 DebugInformation = DebugInformation,
                 UseDebugCRT = UseDebugCRT,

Source/Tools/Flax.Build/Platforms/Windows/WindowsToolchainBase.cs

@@ -467,8 +467,11 @@ namespace Flax.Build.Platforms
                     // Frame-Pointer Omission
                     commonArgs.Add("/Oy");
 
-                    // Whole Program Optimization
-                    commonArgs.Add("/GL");
+                    if (compileEnvironment.WholeProgramOptimization)
+                    {
+                        // Whole Program Optimization
+                        commonArgs.Add("/GL");
+                    }
                 }
                 else
                 {