Unable to load DLL 'FastTreeNative' in Azure Function

### System information

- **OS version/distro**: win10 (10.0.19041 Build 19041)
- **.NET Version (eg., dotnet --info)**: .net core 3.1

### Issue

- **What did you do?**
ML.net 1.5.1
- **What happened?**
It is no issue to run sample code in console app, but it's repeatedly reporting below error when run CreateModel() from a testing azure function:
=============== Training model ===============
[7/16/2020 7:41:11 AM] Executed 'NormalizeFunction' (Failed, Id=64d8e39f-5a8b-40e9-b335-3cf2cbf4ce45)
[7/16/2020 7:41:11 AM] System.Private.CoreLib: Exception while executing function: NormalizeFunction. System.Private.CoreLib: One or more errors occurred. (Unable to load DLL 'FastTreeNative' or one of its dependencies: The specified module could not be found. (Exception from HRESULT: 0x8007007E)). Microsoft.ML.FastTree: Unable to load DLL 'FastTreeNative' or one of its dependencies: The specified module could not be found. (Exception from HRESULT: 0x8007007E).
- **What did you expect?**
It should run without exception as it did in console app

### Source code / logs

Please paste or attach the code or logs or traces that would be helpful to diagnose the issue you are reporting.