[cross-project-tests] Fix struct-dse example so that it fails again (#73566)

The purpose of this example is to provide a case where the debugger /
debug info experience could be improved. A recent commit by clang
(0d2860b7) changed codegen such that it
changes how "small structs" are initialized, in a way that the debugger
is now able to correctly display the variable being targeted by this
test.

In order to keep the example relevant, i.e. failing, this commit makes
it so that the struct is now "big enough" to not trigger the new
codegen.