Support linkmap offsets for the AAPCS64-CAP ABI

Support linkmap offsets for the AAPCS64-CAP ABI

With the AAPCS64-CAP ABI, any pointers in data structures become capabilities.
Capabilities for Morello are 128-bit in size, so the offsets of individual
fields within the structure might change.

One such structure that needs to be adjusted is the linkmap. The linkmap is
used by GDB to list shared libraries that get loaded/unloaded.

This patch enables AAPCS64-CAP linkmap offsets for both GDB and GDBserver,
allowing GDB/GDBserver to list the shared libraries correctly.