tests/tcg/multiarch/Makefile.target: Disable run-gdbstub-sha1 test

tests/tcg/multiarch/Makefile.target: Disable run-gdbstub-sha1 test

Disable the run-gdbstub-sha1 test: it provokes an internal error
assertion failure in Ubuntu gdb 8.1.1-0ubuntu1 (Ubuntu gdb
8.1-0ubuntu3.2 also has this assert but we were previously skipping
this test because it doesn't support connection over local domain
sockets) :

timeout 60  /home/petmay01/linaro/qemu-for-merges/tests/guest-debug/run-test.py --gdb /usr/bin/gdb-multiar
/build/gdb-veKdC1/gdb-8.1.1/gdb/regcache.c:122: internal-error: void* init_regcache_descr(gdbarch*): Asser
A problem internal to GDB has been detected,
further debugging may prove unreliable.

This is a bug, please report it.  For instructions, see:
<http://www.gnu.org/software/gdb/bugs/>.

Aborted (core dumped)
/home/petmay01/linaro/qemu-for-merges/tests/tcg/multiarch/Makefile.target:51: recipe for target 'run-gdbst

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Message-id: 20201214133702.24088-1-peter.maydell@linaro.org