doc-tutorial tests don't always get regenerated?

[catamorphism]

At revision 561511e I got a test failure with test/doc-tutorial/syntax_basics_14.rs:

x86_64-apple-darwin/test/doc-tutorial/syntax_basics_14.rs:3:0: 3:16 error: unresolved modulename: io
x86_64-apple-darwin/test/doc-tutorial/syntax_basics_14.rs:3 std::io::println(#env("PATH"));

Manually deleting the contents of the directory x86_64-apple-darwin/test/doc-tutorial fixed the problem. But the doc-tutorial tests should get rebuilt automatically without having to do that.

[brson]

I believe the problem is that stale tests don't get deleted