I asked an AI to review a patch that added a new file, and it mentioned I
should add an include of defs.h as first include.
That used to be true, but since commit 18d2988e5d ("gdb, gdbserver,
gdbsupport: remove includes of early headers") that's not the case anymore.
Error out when encountering a second include of defs.h, and remove a few of
those.
While we're at it, do the same for gdbsupport/common-defs.h and
gdbserver/server.h.
Tested by rebuilding gdb on x86_64-linux.
V1 submitted here [1].
Changes in v1:
- also handle gdbserver/server.h
- change error message to use "manually" instead of "twice"
Approved-By: Simon Marchi <simon.marchi@efficios.com>
[1] https://sourceware.org/pipermail/gdb-patches/2026-April/226694.html
