Escalate container privileges to workaround Python deadlock

Don't know if this will help, but I'm out of ideas.  During Python
installation, a number of forks of:

/usr/bin/qemu-aarch64 ./python -E -Wi -OO
/var/tmp/portage/dev-lang/python-3.8.6-r1/image/usr/lib/python3.8/compileall.py
-j16 -d /usr/lib/python3.8 -f -x
bad_coding|badsyntax|site-packages|lib2to3/tests/data
/var/tmp/portage/dev-lang/python-3.8.6-r1/image/usr/lib/python3.8

are spawned and deadlock in

futex(0x550435f000, FUTEX_WAIT_BITSET|FUTEX_CLOCK_REALTIME, 0, NULL,
FUTEX_BITSET_MATCH_ANY <unfinished ...>

.gitlab-ci.yml

@@ -13,7 +13,7 @@ default:
     QEMU_ARCH: 'x86_64'
   script: &script
     - 'mkdir debug'
-    - 'buildah bud --pull
+    - 'buildah bud --cap-add SYS_ADMIN
                    --security-opt seccomp=unconfined
                    --ulimit nofile=1048576
                    --build-arg STAGE0_TAG="$CPU"