make it an error to have include dir into blas.ldflags as we don't use them and this could hid other include.

Also make the check about the presence of dynamic lib more strong.

Don't check if their is a dynamic lib their.

That prevents other processes from deleting this dir while it is still empty,
before the files are created in it.
That problem caused intermittent failure of some tests.

problem, but ... it could have been?

This is to remove most of error about deleted file in the buildbot. It don't solve the problem if a process run for more then 1 week.