Why do I get build errors when I compile my site with aspnet_compiler.exe, but not when I VS's build tool?

I have a solution with projects for MVC, testing, data access, etc which builds fine when I click "build" in VS 2010.

When I try to use aspnet_compiler at the command prompt (aspnet_compiler.exe -c -v temp -p \absolute\path\to\my\solution\directory), I get two errors and the build fails!

• C:\myFrameworkPath\Temporary ASP.NET Files\temp\6d21e425\4455c27d\App_Web_y5rq3jcy.0.vb(17): warning BC40056: Namespace or type specified in the Imports 'myExternalLib.Controls' doesn't contain any public member or cannot be found. Make sure the namespace or the type is defined and contains at least one public member. Make sure the imported element name doesn't use any aliases.
• C:\myFrameworkPath\Config\web.config(130): error ASPCONFIG: Could not load type 'System.Data.Entity.Design.AspNet.EntityDesignerBuildProvider'.

NOTE: I want to use aspnet_compiler to implement Luis Rocha's pre building views.

I don't know why this happen (and I would still prefer to have that answer), but it looks like the aspnet_compiler tool does not know where to find the System.Data.Entity.Design.AspNet.EntityDesignerBuildProvider type without explicit instructions in the web.config file. The build routine inside of VS 2010 somehow knows, and I do not understand why aspnet_compiler does not do the same!