Test "github660" does not pass with flambda

[emillon]

Hi,

While debugging flambda-related #3599 I noticed that test github660 fails on 4.10.0+flambda with the following diff:

diff --git a/test/blackbox-tests/test-cases/github660.t/run.t b/test/blackbox-tests/test-cases/github660.t/run.t.corrected
index ef75ae81b..e4d323561 100644
--- a/test/blackbox-tests/test-cases/github660.t/run.t
+++ b/test/blackbox-tests/test-cases/github660.t/run.t.corrected
@@ -10,8 +10,6 @@ When there are explicit interfaces, modules must be rebuilt.
   $ echo 'let _x = 1' >> explicit-interfaces/lib_sub.ml
   $ dune runtest --root explicit-interfaces
   Entering directory 'explicit-interfaces'
-          main alias runtest
-  hello
 
 When there are no interfaces, the situation is the same, but it is not possible
 to rely on these.

I did not investigate what that means, but let's keep it somewhere not to forget.