vscode breakpoints not being hit in TS mocha tests

Hi

I have a boilerplate express project in TS.
My setup is that I run the project and the build tool chain inside a docker container; the goal being simple replication of dev environments across multiple machines.

The container is managed by the following compose definition:

```
services:
node:
image: node:12.18.1
hostname: app-node-dev
command: npm run dev
environment:
- HOME=/home/me/workspace/service-kit/sk-base-nodejs
- NODE_ENV=development
ports:
- 8080:8080
- 18080:18080
- 9222:9222
- 9321:9321
volumes:
- ../..:/home/me/workspace/service-kit/sk-base-nodejs:rw
- /etc/group:/etc/group:ro
- /etc/passwd:/etc/passwd:ro
- /etc/shadow:/etc/shadow:ro
- /tmp:/tmp:rw
user: ${_UID}:${_GID}
working_dir: /home/me/workspace/service-kit/sk-base-nodejs
stdin_open: true
tty: true
restart: unless-stopped
```

Note that I am using the working dir as an exact copy of the absolute path on my host machine.
Previously I was mounting to /workspace but I thought that the unmatching paths may be causing the problem; apparently not.

I mount the passwd/shadow so that I can maintain the file ownership.

I have the following vscode launch configuration to attach to the running app instance:

{
"type": "node",
"request": "attach",
"name": "SK - Attach to Node",
"protocol": "inspector",
"port": 9222,
"restart": true,
"localRoot": "${workspaceFolder}/dist",
"remoteRoot": "/workspace/dist",
"outFiles": [
"${workspaceFolder}/dist/**/*.js"
],
"skipFiles": [
"/**/*.js",
]
},

This works great. I can attach and hit breakpoints as expected.

However the problem is when I execute mocha tests via the following launch configuration:

```
{
"type": "node",
"request": "launch",
"name": "SK - Mocha Tests Bak",
"cwd": "${workspaceRoot}",
"runtimeExecutable": "make",
"runtimeArgs": [
"npm",
"run",
"test-brk"
],
"env": {
"NODE_ENV": "test-external",
},
"port": 9321,
"console": "integratedTerminal",
"internalConsoleOptions": "neverOpen",
"protocol": "inspector",
"sourceMaps": true,
},
```

One key unusual thing here is that I am executing `make npm run test-brk`. This make command translates to a `docker-compose exec` that runs `npm run test-brk` within the running container.

The `test-brk` command in the package.json is defined as:

"test-brk": "mocha --require node_modules/ts-node/register --inspect-brk=0.0.0.0:9321 --debug-brk --exit test/**/*.spec.ts",

When I launch the debug config in vscode the tests launch and execute and pass; but the breakpoints are not hit.

`Breakpoint ignored because generated source not found (source map problem?)`

Here is where things get interesting. The above execution runs the `npm run test-brk` within the container. If I install node on my dev machine and execute `npm run test-brk` from my host then everything works as expected - the tests run and the breakpoints are hit.

In short - it appears that vscode cannot find the source maps if I run mocha from within the container. But the source maps are found if I run mocha from on the host.

Is there something that I am missing that gets generated within the container that vscode cannot access? even though the workspace folder is mounted?

I would really appreciate any input on this.

Node is version 12.18.1
Source map support 0.5.19