gdbstub/next: re-organise and split build I was motivated to sort this out while working on my register API which is target agnostic but ran into the weeds when trying to link up with the gdbstub. This was due to us building gdbstub for every single target we support due to a few ABI sensitive bits that require CPU specific information. This series does a bunch of surgery to break the monolithic file apart into its constituent parts as well as simplify the headers to users can avoid bringing in more dependencies than they need. I had hoped to go all the way and conditionally compile syscalls only for the two ABIs (32 and 64 bit) unfortunately I was unable to the appropriate meson-foo to make that happen. This version is mostly just minor clean-ups and tag updates including a few extra code motion and checkpatch cleanup patches. The biggest change is replacing the probe shell script with a slightly smarter python one and adding Mad's accelops patch. The following patches need review: - gdbstub: split out softmmu/user specifics for syscall handling - testing: probe gdb for supported architectures ahead of time - gdbstub: only compile gdbstub twice for whole build - gdbstub: clean-up indent on gdb_exit