SDK 3.1.100 fails in container on Ubuntu 18.04 host

.NET Core SDK 3.1.100 seems to have issues running inside a container on an Ubuntu 18.04 host. Older SDKs such as 2.2.402 and 3.0.100 work without issue.

## Minimal repro
```bash
$ mkdir demo; cd demo
$ dotnet new console
$ dotnet build

Microsoft (R) Build Engine version 16.4.0+e901037fe for .NET Core
Copyright (C) Microsoft Corporation. All rights reserved.

Restore completed in 23.51 ms for /home/vsonline/workspace/demo/demo.csproj.
/home/vsonline/.dotnet/sdk/3.1.100/Roslyn/Microsoft.CSharp.Core.targets(59,5): error MSB6004: The specified task executable location "/ (deleted)" is invalid. [/home/vsonline/workspace/demo/demo.csproj]

Build FAILED.

/home/vsonline/.dotnet/sdk/3.1.100/Roslyn/Microsoft.CSharp.Core.targets(59,5): error MSB6004: The specified task executable location "/ (deleted)" is invalid. [/home/vsonline/workspace/demo/demo.csproj]
0 Warning(s)
1 Error(s)

Time Elapsed 00:00:00.78
```

## Switch to 2.2.402 SDK and it works
```bash
$ mkdir demo; cd demo
$ dotnet new globaljson --sdk-version 2.2.402
$ dotnet new console
$ dotnet build

Microsoft (R) Build Engine version 16.2.32702+c4012a063 for .NET Core
Copyright (C) Microsoft Corporation. All rights reserved.

Restore completed in 42.16 ms for /home/vsonline/workspace/demo/demo.csproj.
demo -> /home/vsonline/workspace/demo/bin/Debug/netcoreapp2.2/demo.dll

Build succeeded.
0 Warning(s)
0 Error(s)

Time Elapsed 00:00:01.09
```

## Dotnet --info
```bash
$ dotnet --info
.NET Core SDK (reflecting any global.json):
Version: 3.1.100
Commit: cd82f021f4

Runtime Environment:
OS Name: debian
OS Version: 9
OS Platform: Linux
RID: debian.9-x64
Base Path: /home/vsonline/.dotnet/sdk/3.1.100/

Host (useful for support):
Version: 3.1.0
Commit: 65f04fb6db

.NET Core SDKs installed:
1.1.14 [/home/vsonline/.dotnet/sdk]
2.1.802 [/home/vsonline/.dotnet/sdk]
2.2.402 [/home/vsonline/.dotnet/sdk]
3.0.100 [/home/vsonline/.dotnet/sdk]
3.1.100 [/home/vsonline/.dotnet/sdk]

.NET Core runtimes installed:
Microsoft.AspNetCore.All 2.1.13 [/home/vsonline/.dotnet/shared/Microsoft.AspNetCore.All]
Microsoft.AspNetCore.All 2.2.7 [/home/vsonline/.dotnet/shared/Microsoft.AspNetCore.All]
Microsoft.AspNetCore.App 2.1.13 [/home/vsonline/.dotnet/shared/Microsoft.AspNetCore.App]
Microsoft.AspNetCore.App 2.2.7 [/home/vsonline/.dotnet/shared/Microsoft.AspNetCore.App]
Microsoft.AspNetCore.App 3.0.0 [/home/vsonline/.dotnet/shared/Microsoft.AspNetCore.App]
Microsoft.AspNetCore.App 3.1.0 [/home/vsonline/.dotnet/shared/Microsoft.AspNetCore.App]
Microsoft.NETCore.App 1.1.13 [/home/vsonline/.dotnet/shared/Microsoft.NETCore.App]
Microsoft.NETCore.App 2.1.13 [/home/vsonline/.dotnet/shared/Microsoft.NETCore.App]
Microsoft.NETCore.App 2.2.7 [/home/vsonline/.dotnet/shared/Microsoft.NETCore.App]
Microsoft.NETCore.App 3.0.0 [/home/vsonline/.dotnet/shared/Microsoft.NETCore.App]
Microsoft.NETCore.App 3.1.0 [/home/vsonline/.dotnet/shared/Microsoft.NETCore.App]

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

## OS
```bash
$ uname -srv
Linux 5.0.0-1027-azure #29~18.04.1-Ubuntu SMP Mon Nov 25 21:18:57 UTC 2019
```

## Other
The 3.1.100 SDK was installed via the following script inside of a VS Online environment, which is running inside a Debian 9 container on an Ubuntu 18.04 host:
```bash
wget -q https://dot.net/v1/dotnet-install.sh -O dotnet-install.sh
chmod +x dotnet-install.sh
./dotnet-install.sh --version 3.1.100
rm dotnet-install.sh
```