tests: do not assume compiler prefers shared libraries.

Testing whether -static-libtool-libs causes a non-libtool library to be
linked dynamically is effectively a test of the compiler's preference in
this case.  The Cray compiler prefers static libraries if not told
otherwise.
* tests/static.at [static linking flags for programs]: Do not expect
 -static-libtool-libs to fail.

Signed-off-by: Gary V. Vaughan <gary@gnu.org>