Is there a way to display the build time of an entire solution in Visual Studio?

EDIT: Here's a way you can write the build time directly to the build window.

Open the Visual Studio Macro IDE.
Navigate to MyMacros > EnvironmentEvents.
Under MyMacros, add a reference to System.Windows.Forms (for the code below to show a popup window).
Add this code to the EnvironmentEvents module:

Dim buildStart As Date

Private Function IsBuild(ByVal scope As EnvDTE.vsBuildScope, ByVal action As EnvDTE.vsBuildAction) As Boolean
    Return scope = vsBuildScope.vsBuildScopeSolution AndAlso (action = vsBuildAction.vsBuildActionBuild OrElse action = vsBuildAction.vsBuildActionRebuildAll)
End Function

Private Sub BuildEvents_OnBuildBegin(ByVal Scope As EnvDTE.vsBuildScope, ByVal Action As EnvDTE.vsBuildAction) Handles BuildEvents.OnBuildBegin
    If (IsBuild(Scope, Action)) Then
        buildStart = Date.Now
    End If
End Sub

Private Sub BuildEvents_OnBuildDone(ByVal Scope As EnvDTE.vsBuildScope, ByVal Action As EnvDTE.vsBuildAction) Handles BuildEvents.OnBuildDone
    If (IsBuild(Scope, Action)) Then
        Dim buildTime = Date.Now - buildStart
        WriteToBuildWindow(String.Format("Build time: {0}", buildTime.ToString))
    End If
End Sub

Private Sub WriteToBuildWindow(ByVal message As String)
    Dim win As Window = DTE.Windows.Item(EnvDTE.Constants.vsWindowKindOutput)
    Dim ow As OutputWindow = CType(win.Object, OutputWindow)
    For Each owPane As OutputWindowPane In ow.OutputWindowPanes
        If (owPane.Name.Equals("Build")) Then
            owPane.OutputString(message)
            Exit For
        End If
    Next
End Sub

When you build or rebuild the full solution, at the end, the build/rebuild duration will be printed to the build output window. You can change the conditions in IsBuild to suit your preferences.

Tools->Options->Projects and Solutions->VC++ Project Settings->Build Timing

That's an old question but I thought some may still find it useful.

I have written an extension for VS2015 and VS2017. It displays the start and end time for each project, expressed relative to the start of the overall build. Hence the end time of the last project is the total build time for the solution.

I have posted more about the extension here.