Version Used:
Using dotnet SDK 2.2.0-preview1-007866 on macOS 10.13.2

Steps to Reproduce:
TBH not sure 100% how to get into bad state. I don't know what is launching VBCSCompiler.dll. The parent process is gone...which is the issue.

But, it has been happening fairly often over the last few days while working on the https://github.com/dotnet/cli repo using VS Code - Insiders + C# extension 1.13.1.

If someone can point me to how to capture more information about how this long-running compiler server starts, I can provide a better repro.

Expected Behavior:
No long running compiler process after I shutdown tools and build scripts.

Actual Behavior:

VS Code is closed, and I've killed the the build.sh script, yet I have two VBCSCompiler processes running. ps reports the processes have been open for ~ 18 hours.

The process was launched with these arguments:

/Users/namc/.dotnet/dotnet /Users/namc/.dotnet/sdk/2.2.0-preview1-007866/Roslyn/bincore/VBCSCompiler.dll -pipename:namc.False.bZ9mpL2HFmG8IVwxPkEmz6_N4OMYW1cLZOeZGRjGfv0

Process sample:
processample.txt

[EDIT]

See below for a workaround: #24137 (comment)