scripts/clone.sh: Install python3-venv via apt-get

This unbreaks OpenCI after
https://review.trustedfirmware.org/c/ci/tf-a-ci-scripts/+/12536
was merged.

It goes with the following comment:

WORKAROUND START
Install last-minute dependencies. This should not be done like that,
instead all dependencies should go into the build docker image. But
to unbreak urgent regressions, some packages may be installed here
until they're moved to the docker image.
WORKAROUND END

Signed-off-by: Paul Sokolovsky <paul.sokolovsky@linaro.org>
Change-Id: If430c0f62be0c40e3c85fd94f6077562d0c30732
diff --git a/scripts/clone.sh b/scripts/clone.sh
index e344cf3..6d1203b 100755
--- a/scripts/clone.sh
+++ b/scripts/clone.sh
@@ -27,6 +27,15 @@
 
 set -e
 
+# WORKAROUND START
+# Install last-minute dependencies. This should not be done like that,
+# instead all dependencies should go into the build docker image. But
+# to unbreak urgent regressions, some packages may be installed here
+# until they're moved to the docker image.
+sudo apt update
+sudo apt-get install -y python3-venv
+# WORKAROUND END
+
 # Global defaults
 REFSPEC_MASTER="refs/heads/master"
 GIT_REPO="https://git.trustedfirmware.org"