tests/int: ability to specify binary

This can be used to specify a different runc binary, for example:

	sudo -E RUNC=$PWD/runc.mine tests/integration/cwd.bats

A different (but compatible enough) runtime also works:

	sudo -E RUNC=/usr/local/bin/crun tests/integration/cwd.bats

Signed-off-by: Kir Kolyshkin <kolyshkin@gmail.com>

tests/integration/helpers.bash

@@ -14,7 +14,7 @@ IMAGES=$("${INTEGRATION_ROOT}"/get-images.sh)
 eval "$IMAGES"
 unset IMAGES
 
-RUNC="${INTEGRATION_ROOT}/../../runc"
+: "${RUNC:="${INTEGRATION_ROOT}/../../runc"}"
 RECVTTY="${INTEGRATION_ROOT}/../../contrib/cmd/recvtty/recvtty"
 SD_HELPER="${INTEGRATION_ROOT}/../../contrib/cmd/sd-helper/sd-helper"
 SECCOMP_AGENT="${INTEGRATION_ROOT}/../../contrib/cmd/seccompagent/seccompagent"
@@ -47,7 +47,7 @@ function runc() {
 	# Some debug information to make life easier. bats will only print it if the
 	# test failed, in which case the output is useful.
 	# shellcheck disable=SC2154
-	echo "runc $* (status=$status):" >&2
+	echo "$(basename "$RUNC") $* (status=$status):" >&2
 	# shellcheck disable=SC2154
 	echo "$output" >&2
 }