'--no-build' flag messes with 'dotnet run' error messages

[liebasam]

Describe the bug

Calling 'dotnet run --no-build ' on a project file that doesn't exist produces the error message:

is not a valid project file.

Just spent hours trying to debug why running the project locally worked just fine, but stopped working in a CI setting. The message leads one to believe its an issue with the csproj file or environment, when in reality the file just doesn't exist. (In my case, underlying cuase was a double quoting issue)

For whatever reason, removing the '--no-build' flag makes for a better message:

Project file does not exist.

To Reproduce

Version 5.0.403 of .NET SDK. Reproduced on Windows 10 + Debian 10

> dotnet run --project xyz.csproj
MSBUILD : error MSB1009: Project file does not exist.
Switch: xyz.csproj

The build failed. Fix the build errors and run again.

> dotnet run --project xyz.csproj --no-build
'xyz.csproj' is not a valid project file.

Further technical details

.NET SDK (reflecting any global.json):
 Version:   5.0.403
 Commit:    bf9d168ac2

Runtime Environment:
 OS Name:     debian
 OS Version:  10
 OS Platform: Linux
 RID:         debian.10-x64
 Base Path:   <network location at my job>

Host (useful for support):
  Version: 5.0.12
  Commit:  7211aa01b3

[marcpopMSFT]

Triage: It's potentially challenging to route the exception correctly but we can probably do an exists check on the project before we try to access it. Let's see if copilot can identify that.