Description:
msbuild vsintegration\fsharp-vsintegration-build.proj (debug) fails with FS3180 warnings

Repro Steps:
Go through the steps of the devguide "3. Full Steps Before Running Tests" (debug).

Expected:
The build succeeds.

Actual:
The build fails.

Severity: medium?

Version: Microsoft/visualfsharp:master fd4d36f

Likely Cause:
Warnings are generated in tast.fs lines 38 and 43 because /warnon:3180 is explicitly set for debug in FSharpSource.settings.target.
Strange that it is set only for debug builds...