toolchain/54820: gdb broken

[martin%NetBSD.org@localhost]

>Number:         54820
>Category:       toolchain
>Synopsis:       gdb broken
>Confidential:   no
>Severity:       critical
>Priority:       high
>Responsible:    toolchain-manager
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Wed Jan 01 11:20:00 +0000 2020
>Originator:     Martin Husemann
>Release:        NetBSD 9.99.31
>Organization:
The NetBSD Foundation, Inc.
>Environment:
System: NetBSD space-truckin.duskware.de 9.99.31 NetBSD 9.99.31 (GENERIC) #30: Tue Dec 31 14:55:51 CET 2019 martin%seven-days-to-the-wolves.aprisoft.de@localhost:/work/src/sys/arch/evbarm/compile/GENERIC evbarm
Architecture: earmv7hfeb
Machine: evbarm
>Description:

Trying to attach to a life process and getting a backtrace
fails:

# gdb -p 695
GNU gdb (GDB) 8.3
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Attaching to process 695
Reading symbols from /usr/tests/kernel/h_ps_strings2...
Reading symbols from /usr/libdata/debug//usr/tests/kernel/h_ps_strings2.debug...
Reading symbols from /usr/lib/libc.so.12...
Reading symbols from /usr/libdata/debug//usr/lib/libc.so.12.214.debug...
Reading symbols from /usr/libexec/ld.elf_so...
Reading symbols from /usr/libdata/debug//usr/libexec/ld.elf_so.debug...
[Switching to LWP 1 of process 695]
0x792fa1bc in _sys___nanosleep50 () from /usr/lib/libc.so.12
(gdb) bt
#0  0x792fa1bc in _sys___nanosleep50 () from /usr/lib/libc.so.12
terminate called after throwing an instance of 'gdb_exception_RETURN_MASK_ERROR'
#1  0x79235a04 in _sleep (

and then gdb hangs (the incomplete line is not a copy + paste error when
filling this PR).

>How-To-Repeat:
not sure, gdb -p to a non-threaded process in -current on evbarmv7hf-eb?

>Fix:
n/a