c++: Add testcase for this PR [PR97990]

This testcase was fixed by r14-5934-gf26d68d5d128c8 but we should add
one to make sure it does not regress again.

Committed as obvious after a quick test on the testcase.

	PR c++/97990

gcc/testsuite/ChangeLog:

	* g++.dg/torture/vector-struct-1.C: New test.

Signed-off-by: Andrew Pinski <quic_apinski@quicinc.com>