Sorry I don't have time to look further at it now but thought I'd post
it here so it's easier to see - the latest ports build on sparc64
failed,

http://build-failures.rhaalovely.net/sparc64/2020-02-19/devel/got,-main.log

/usr/bin/make -C gotweb
yacc -d -o parse.c parse.y
cc -O2 -pipe -Werror -Wall -Wstrict-prototypes -Wunused-variable  -MD -MP  -DGOT_TMPDIR=/got/tmp -I/usr/obj/ports/got-0.26/got-0.26/gotweb/../include -I/usr/obj/ports/got-0.26/got-0.26/gotweb/../lib -I/usr/obj/ports/got-0.26/got-0.26/gotweb  -I/usr/local/include -DGOT_LIBEXECDIR=/cgi-bin/gotweb/libexec -DGOT_VERSION=0.26 -nostdinc -idirafter /usr/include -c gotweb.c
cc1: warnings being treated as errors
gotweb.c: In function 'gw_tag':
gotweb.c:1487: warning: 'kerr' may be used uninitialized in this function
*** Error 1 in gotweb (<sys.mk>:87 'gotweb.o')
===> Exiting devel/got,-main with an error

The warning makes no sense to me, but maybe the simplest approach would
just be to avoid -Werror in ports build?

FWIW gcc8 builds fail earlier, like so:

/usr/obj/ports/got-0.27/got-0.27/libexec/got-read-blob/../../lib/privsep.c: In function 'got_privsep_recv_gitconfig_remotes':
/usr/obj/ports/got-0.27/got-0.27/libexec/got-read-blob/../../lib/privsep.c:1509:13: error: 'iremotes.nremotes' may be used uninitialized in this function [-Werror=maybe-uninitialized]
  *remotes = recallocarray(NULL, 0, iremotes.nremotes, sizeof(iremote));
             ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
cc1: all warnings being treated as errors