ci: isolate the home directory for test execution

libgit2 can now isolate its home directory, and our test runner (by
default) isolates the home directory. In our CI environment, we want to
set up some pieces (like ssh configuration) in a fake homedir. Continue
to do so and propagate that to clar.

ci/test.sh

@@ -16,6 +16,9 @@ BUILD_DIR=$(pwd)
 TMPDIR=${TMPDIR:-/tmp}
 USER=${USER:-$(whoami)}
 
+HOME=`mktemp -d ${TMPDIR}/home.XXXXXXXX`
+export CLAR_HOMEDIR=${HOME}
+
 SUCCESS=1
 CONTINUE_ON_FAILURE=0
 
@@ -140,7 +143,6 @@ fi
 
 if [ -z "$SKIP_SSH_TESTS" ]; then
 	echo "Starting SSH server..."
-	HOME=`mktemp -d ${TMPDIR}/home.XXXXXXXX`
 	SSHD_DIR=`mktemp -d ${TMPDIR}/sshd.XXXXXXXX`
 	git init --bare "${SSHD_DIR}/test.git" >/dev/null
 	cat >"${SSHD_DIR}/sshd_config" <<-EOF