Prevent erroneous copying of the data section

With __data_load declared outside the .data section, lld doesn't put
__data_load and __data_start at the same address; they differ by 16
bytes. This tricks the runtime's initialization code into thinking that
it needs to copy the data section, effectively breaking it.

Issue: eng/toolchain/gnat-llvm#64

aarch64/morello/common.ld

@@ -146,9 +146,9 @@ SECTIONS
  *(.got)
  } > REGION_DATA
 
- __data_load = .;
- .data : AT (__data_load)
+ .data :
  {
+ __data_load = .;
  __data = .;
  __data_start = .;
  *(.data .gnu.linkonce.d*)