Ensure that compiler path is set during Design Time build

[KevinRansom]

In order to deploy the compiler with the VS tools VSIX, the IDE sets a build global variable: FSharpCompilerPath, the build targets then use this to target the correct compiler.

The design time build wasn't picking up this value, and therefore using the compiler shipped with VS for Intellisense etc. The end result was that MSBuild was using the old version of the FSharp.Build build task.

Because MsBuild was then reused for the re-build when doing a rebuild with the correct compiler tools path, msbuild silently used the already loaded FSharp.Build task, and failed to correctly bind to the EmbeddedFiles property.

Fortunately the Fix was trivial, and we now know a small amount more about the BuildTargets.

Kevin

[brettfo]

The internal source of ExportBuildGlobalPropertiesProvider shows that the boolean you specify switches between string values of "Microsoft.VisualStudio.ProjectSystem.DesignTimeBuild" and "Microsoft.VisualStudio.ProjectSystem.FullBuild" and the comments seem to indicate that the two values are mutually exclusive. Because of that can you do one extra check to ensure that the regular IDE build has that property set, too? I don't want to trade one bug for another.

[cartermp]

@KevinRansom This addresses #5640 yes?

[KevinRansom]

@brettfo sure can, I'm still doing a bit more testing anyway.@cartermp yeppers.

[KevinRansom]

@brettfo, @cartermp this change relies on the project system bug being fixed. I believe that fix is targeted at release 15.8.6.

Because this change is in our code, we do not need to propagate a fix to the release branch until Dev16. It is sufficient that nightlies have this code.

Kevin

[cartermp]

Sounds good. I set the milestone for #5640 to be 16.0.

[KevinRansom]

@brettfo good eyes, mate.