[ARM32]With .NET 5 SDK installed, running application failed with error required library libhostfxr.so could not be found.

Repro steps:

1. Prepare Ubuntu20.04 container on ARM32.
2. Install .NET 5 SDK with ARM Binaries(tar -xf dotnet-sdk-5.0.403-linux-arm.tar.gz, installation path: “/root/mytest”).
3. Create a new console app and try to run it.

Expected Result: App could be run successfully.

Actual Result: Running app failed with error required library libhostfxr.so could not be found.

root@4eb6957f9afc:~/myconsole# dotnet run
A fatal error occurred. The required library libhostfxr.so could not be found.
If this is a self-contained application, that library should exist in [/root/myconsole/bin/Debug/net5.0/].
If this is a framework-dependent application, install the runtime in the global location [/usr/share/dotnet] or use the DOTNET_ROOT environment variable to specify the runtime location or register the runtime location in [/etc/dotnet/install_location].

The .NET runtime can be found at:
  - https://aka.ms/dotnet-core-applaunch?missing_runtime=true&arch=arm&rid=ubuntu.20.04-arm&apphost_version=5.0.12

Note:

1. After manually set DOTNET_ROOT, it can be run successfully.
2. It was not repro on ARM64

Dotnet info:

root@4eb6957f9afc:~/mytest# dotnet --info
.NET SDK (reflecting any global.json):
 Version:   5.0.403
 Commit:    cd8226c2c5

Runtime Environment:
 OS Name:     ubuntu
 OS Version:  20.04
 OS Platform: Linux
 RID:         ubuntu.20.04-arm
 Base Path:   /root/mytest/sdk/5.0.403/

Host (useful for support):
  Version: 5.0.12
  Commit:  88faabc950

.NET SDKs installed:
  5.0.403 [/root/mytest/sdk]

.NET runtimes installed:
  Microsoft.AspNetCore.App 5.0.12 [/root/mytest/shared/Microsoft.AspNetCore.App]
  Microsoft.NETCore.App 5.0.12 [/root/mytest/shared/Microsoft.NETCore.App]

To install additional .NET runtimes or SDKs:
  https://aka.ms/dotnet-download

[vitek-karas]

@ericstj I think we raced to answer this one - I’m pretty sure it’s the bug in dotnet run as mentioned above.

To verify the theory, set DOTNET_ROOT so that the app starts, and print out Environment.GetEnvironmentVariable("DOTNET_ROOT(x86)") - this should never be set on Linux, but I would bet it’s set this time.

[vitek-karas]

Correct - this should affect all arm32 private installs for 3.1/5.0.