The new resolution-based LTO API leads to global variables being re-ordered
during module merging for regular LTO. With the old LTO API and in the non-LTO
case, the source order is preserved.
The new order is semi-random; it is caused by recursively materializing
variables as their uses are discovered during materialization of functions. In
practice, it is often the exact reverse of source order.
While the C standard makes no guarantee about the relative ordering of global
variables, there is no discernable benefit to re-ordering them in this way.
Worse, it can negatively affect performance by degrading cache locality and
introduces unnecessary variation in behavior and performance between the two
LTO APIs, and the non-LTO case.
This fixes PR32441.