Obscure error message when building in root directory

When building a docker image, if I forget the `WORKDIR` command, I build in the root directory. When I build, I get a really obscure error:

`/usr/share/dotnet/sdk/2.1.301/Microsoft.Common.CurrentVersion.targets(3045,5): error MSB3552: Resource file "**/*.resx" cannot be found.`

This message could be clearer in helping me discover the problem

### Steps to reproduce

0. Create empty directory in a convenient location.

1. `dotnet new mvc --framework=netcoreapp2.1 -n mything -o .`

2. Create Dockerfile:

```
FROM microsoft/dotnet:2.1-sdk-alpine AS build

# Oops: forgot this line: WORKDIR /src

COPY . .
RUN dotnet build mything.csproj -c Release
```

3. `docker build .`

### Expected behavior

A message that explains that building at `/` isn't supported.

### Actual behavior

A confusing message about `**/*.resx`. This message makes no sense because my project doesn't include any resx files.

OS info:

dotnet --version
// 2.1.300

docker --version
// Docker version 18.05.0-ce, build f150324

OS: Windows 10 v. 1803

Docker in Linux mode