scripts/repo-install-test: fix sftp compat

When running scp, Debian 12 uses the SFTP protocol by default instead of
the legacy SCP protocol. For some reason, this means it doesn't create
the /repo-install-test directory inside QEMU:

  + … scp … -r scripts/repo-install-test root@127.0.0.1:/repo-install-test
  Warning: Permanently added '[127.0.0.1]:22793' (ED25519) to the list of known hosts.
  scp: realpath /repo-install-test: No such file
  scp: upload "/repo-install-test": path canonicalization failed
  scp: failed to upload directory scripts/repo-install-test to /repo-install-test

Changing to the legacy protocol with "scp -O" would make it work again,
but instead of doing that add the mkdir so it works with the new
protocol too.

Related: OS#6186
Change-Id: I740affad2ea794094c8faa89a89bcad094e0075d
---
M scripts/repo-install-test.sh
1 file changed, 25 insertions(+), 0 deletions(-)

diff --git a/scripts/repo-install-test.sh b/scripts/repo-install-test.sh
index 246d5e5..98f0176 100755
--- a/scripts/repo-install-test.sh
+++ b/scripts/repo-install-test.sh
@@ -153,6 +153,7 @@
 	EOF
 
 	qemu_ssh rm -rf /repo-install-test/
+	qemu_ssh mkdir /repo-install-test
 	qemu_scp -r "$TEST_DIR" "root@127.0.0.1:/repo-install-test"
 
 	TIMEOUT="1h" qemu_ssh sh -ex /repo-install-test/run-inside-env.sh

