UPM authentication and runAsHostUser on self-hosted linux runner

**Bug description**

I created a self-hosted Linux runner for GitHub, to build my unity app. When I set the unity-builder `runAsHosteUser` to true authentication to UPM Server fails:
```
An error occurred while resolving packages:
Project has invalid dependencies:
com.neobird.bootstrap: Request [GET ] failed because it lacks valid authentication credentials
```

**How to reproduce**

Install Linux runner like described on:
https://game.ci/docs/self-hosting/host-provisioning/ubuntu-setup

Use these two steps:
```yaml
- name: Setup UPM Authentication
timeout-minutes: 10
run: |
mkdir ${{ runner.temp }}/_github_home
cd ${{ runner.temp }}/_github_home
echo "[npmAuth.\"my verdaccio url"]" >> .upmconfig.toml
echo "alwaysAuth = true" >> .upmconfig.toml
echo "token = \"${{ secrets.NPM_AUTH_TOKEN }}\"" >> .upmconfig.toml

```
and
```yaml
- name: Unity Build (${{ matrix.targetPlatform }}, ${{ matrix.buildProfile }}, ${{ matrix.unityVersion }})
uses: game-ci/unity-builder@v4
timeout-minutes: 60
env:
UNITY_SERIAL: ${{ secrets.UNITY_SERIAL }}
UNITY_EMAIL: ${{ secrets.UNITY_EMAIL }}
UNITY_PASSWORD: ${{ secrets.UNITY_PASSWORD }}
with:
runAsHostUser: ${{ matrix.runAsHostUser }}
versioning: Semantic
dockerWorkspacePath: /github/workspace
unityVersion: ${{ matrix.unityVersion }}
targetPlatform: ${{ matrix.targetPlatform }}
buildMethod: NeoBird.Build.BuildScript
customParameters: '-buildProfile ${{ matrix.buildProfile }
```

`matrix.runAsHostUser` of course is true.

**Expected behavior**

UPM packages should be resolved.

Maybe it's because of step Setup, UPM Authentication does not run as HostUser.
Thx for your help.

Start by comparing the Setup UPM Authentication step with the unity-builder@v4 step when runAsHostUser is true, using the self-hosted Ubuntu setup as context. Reproduce the workflow and verify that the UPM package request succeeds with valid authentication credentials while running as the host user.

Written by the indexing model from the issue text.