targets(59, 5): error MSB6004 in Ubuntu emulator in termux

I installed Ubuntu 20.04 LTS in termux, and manually installed `dotnet` according to the [instructions](https://dotnet.microsoft.com/download/dotnet-core/thank-you/sdk-3.1.100-preview3-linux-arm64-binaries).

When I ran `dotnet`, everything was OK. However, when I created a console app with `dotnet new console -o myApp` and ran it with `dotnet run`, an error happened:

> /root/dotnet/sdk/3.1.100/Roslyn/Microsoft.CSharp.Core.targets(59, 5): error MSB6004: The specified task executable location "/data/data/com.termux/files/home/ubuntu-fs/root/dotnet/dotnet" is invalid. [/root/cs/myApp/myApp.csproj]

Why this happens?