pkg/55306: Pkgsrc bootstrap failure with gcc 10

[triaxx%netbsd.org@localhost]

>Number:         55306
>Category:       pkg
>Synopsis:       Pkgsrc bootstrap failure with gcc 10
>Confidential:   no
>Severity:       serious
>Priority:       low
>Responsible:    pkg-manager
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Wed May 27 09:20:00 +0000 2020
>Originator:     Frédéric Fauberteau
>Release:        Linux 5.6.13-arch1-1 x86_64 | pkgsrc-HEAD
>Organization:
>Environment:
System: Linux guardian 5.6.13-arch1-1 #1 SMP PREEMPT Thu, 14 May 2020 06:52:53 +0000 x86_64 GNU/Linux
Architecture: x86_64
Machine: amd64
Compiler: gcc (GCC) 10.1.0
>Description:
$ ./bootstrap --cwrappers no --prefer-pkgsrc yes --unprivileged --workdir /tmp/pkgsrc

produces the following errors:

===> Building for pax-20080110nb4
[...]
cc -L/tmp/pkgsrc/wrk/archivers/pax/work/libnbcompat -Wl,-R/home/triaxx/pkg/lib -o pax ar_io.o ar_subs.o buf_subs.o file_subs.o ftree.o  gen_subs.o getoldopt.o options.o pat_rep.o pax.o sel_subs.o tables.o  tar.o tty_subs.o  getid.o spec.o misc.o stat_flags.o pack_dev.o cpio.o -lutil -lnbcompat
/usr/bin/ld: ar_subs.o:(.bss+0x24e8): multiple definition of `chdname'; ar_io.o:(.bss+0x20): first defined here
/usr/bin/ld: buf_subs.o:(.bss+0x20): multiple definition of `chdname'; ar_io.o:(.bss+0x20): first defined here
/usr/bin/ld: file_subs.o:(.bss+0x8): multiple definition of `chdname'; ar_io.o:(.bss+0x20): first defined here
/usr/bin/ld: ftree.o:(.bss+0x0): multiple definition of `chdname'; ar_io.o:(.bss+0x20): first defined here
/usr/bin/ld: gen_subs.o:(.bss+0x0): multiple definition of `chdname'; ar_io.o:(.bss+0x20): first defined here
/usr/bin/ld: getoldopt.o:(.bss+0x0): multiple definition of `chdname'; ar_io.o:(.bss+0x20): first defined here
/usr/bin/ld: options.o:(.bss+0x0): multiple definition of `chdname'; ar_io.o:(.bss+0x20): first defined here
/usr/bin/ld: pat_rep.o:(.bss+0x0): multiple definition of `chdname'; ar_io.o:(.bss+0x20): first defined here
/usr/bin/ld: pax.o:(.bss+0x130): multiple definition of `chdname'; ar_io.o:(.bss+0x20): first defined here
/usr/bin/ld: sel_subs.o:(.bss+0x0): multiple definition of `chdname'; ar_io.o:(.bss+0x20): first defined here
/usr/bin/ld: tables.o:(.bss+0x0): multiple definition of `chdname'; ar_io.o:(.bss+0x20): first defined here
/usr/bin/ld: tar.o:(.bss+0x28): multiple definition of `chdname'; ar_io.o:(.bss+0x20): first defined here
/usr/bin/ld: tty_subs.o:(.bss+0x0): multiple definition of `chdname'; ar_io.o:(.bss+0x20): first defined here
/usr/bin/ld: cpio.o:(.bss+0x8): multiple definition of `chdname'; ar_io.o:(.bss+0x20): first defined here
collect2: error: ld returned 1 exit status
*** [pax] Error code 1
>How-To-Repeat:
>Fix: