[dev] Automatically configure the DOTNET_REFERENCE_ASSEMBILES_PATH variable if it not set.

[troydai]

The variable is required by dotnet to compile projects which target desktop CLR. It’s usually missing on most environment. Once it is missing Roslyn will fail to resolve any BCL types and there is no intuitive error or warning for user to correct their environment.

[troydai]

Alternative solution: Fail and send warning early if mono is missing.

[analogrelay]

I'd suggest closing this without fixing in favor of fixing https://github.com/dotnet/cli/issues/531

[troydai]

Issue is fixed on dotnet-cli. Now OmniSharp needs to update its dependencies to leverage the fix.

[troydai]

Fixed in 952c3fd