Use JSON serialization for balena build secrets

Build secrets make use of a `volumes` option passed to the build image
docker API. This option is only available in balenaEngine. With the
changes on apocas/docker-modem#181, this array will be serialized using
URL serialization by dockerode, which is not accepted by balenaEngine.

Change-type: patch

Author: pipex

lib/multibuild/build-secrets/index.ts

@@ -146,7 +146,7 @@ export async function populateSecrets(
 	const imageName = 'balena-secrets:latest';
 	const dockerOpts = {
 		t: imageName,
-		volumes: [`${tmpDir}:${tmpDir}:rw`],
+		volumes: JSON.stringify([`${tmpDir}:${tmpDir}:rw`]),
 		forcerm: true,
 	};
 	const builder = Builder.fromDockerode(docker);
@@ -206,7 +206,7 @@ export async function removeSecrets(
 	const imageName = 'balena-secrets-remove:latest';
 	const dockerOpts = {
 		t: imageName,
-		volumes: [`${tmpDir}:${tmpDir}:rw`],
+		volumes: JSON.stringify([`${tmpDir}:${tmpDir}:rw`]),
 		forcerm: true,
 	};
 	const builder = Builder.fromDockerode(docker);