[.NET] Mention MSBuild panel when building fails

modules/mono/editor/GodotTools/GodotTools/Build/BuildManager.cs

@@ -230,7 +230,7 @@ namespace GodotTools.Build
 
             if (!success)
             {
-                ShowBuildErrorDialog("Failed to build project");
+                ShowBuildErrorDialog("Failed to build project. Check MSBuild panel for details.");
             }
 
             return success;

modules/mono/editor/GodotTools/GodotTools/Export/ExportPlugin.cs

@@ -286,7 +286,7 @@ namespace GodotTools.Export
                     if (!BuildManager.PublishProjectBlocking(buildConfig, platform,
                             runtimeIdentifier, publishOutputDir, includeDebugSymbols))
                     {
-                        throw new InvalidOperationException("Failed to build project.");
+                        throw new InvalidOperationException("Failed to build project. Check MSBuild panel for details.");
                     }
 
                     string soExt = ridOS switch