[lld] [lld] Add target support for SystemZ (s390x) (PR #75643)

[Ulrich Weigand via llvm-commits]

uweigand wrote:

```
ld.lld: error: section .ipldata virtual address range overlaps with .head.text
>>> .ipldata range is [0x38, 0x237]
>>> .head.text range is [0x200, 0x102CF]
```

Hmm, this looks like a real problem.  Looking at the linker script (boot/vmlinux.lds.S): 
```
SECTIONS
{
        . = 0;
        .ipldata : {
                *(.ipldata)
        }
        . = IPL_START;
        .head.text : {
                _head = . ;
                HEAD_TEXT
                _ehead = . ;
        }
        . = PARMAREA;
        .parmarea : {
                *(.parmarea)
        }
```
the `.ipldata` section *should* be residing at [0x0, 0x1ff], which apparently it isn't.  Everything else seems to be follow-on problems.

Not sure why lld doesn't appear to respect the `. = 0` setting here.



https://github.com/llvm/llvm-project/pull/75643