[lld/MachO] Fix assert on unsorted data-in-code entries (#81758)

When the data-in-code entries are in separate sections, they are not
guaranteed to be sorted. In particular, 68b1cc36f3df marked some libc++
string functions as noinline, which leads to global ctors involving
strings now producing data-in-code sections in __TEXT,__StaticInit,
which is why this now happens in practice.

Since data-in-code entries are relatively rare and small, just sort
them. No observed performance impact.

See also crbug.com/41487860