buildOptions does not merge correctly

Steps to reproduce

Write a project.json that uses multiple buildOptions objects, one under root, and one under a particular framework, e.g.:

{
    "buildOptions": {
        "compile": {
            "include": [ "some", "goodFiles" ]
        }
    },

    "frameworks": {
        "netstandard1.5": {
            "buildOptions": {
                "compile": {
                    "exclude": [ "other", "badFiles" ]
                }
            }
        }
    }
}

Expected behavior

Both include and exclude to be respected for dotnet build -c netstandard1.5, that is, the root included files to be included, and the framework excluded files to be excluded (the objects are merged).

This is inline with the proposal https://github.com/dotnet/core-proposals/pull/15 for the schema update https://github.com/aspnet/Announcements/issues/175 implemented in https://github.com/dotnet/cli/pull/2493.

The "buildOptions" section can be defined in:

• the root of the project file, in which case the properties apply whenever compiling the project
• under an entry in the “configurations” section, in which case the properties apply when compiling with that configuration
• under an entry in the “frameworks” section, in which case the properties apply when compiling for that framework

(Added emphasis my own.)

Actual behavior

Only the buildOptions properties under the framework is respected, thus those files are excluded, but the root included files are not included.

Currently, the only way to get the intended behavior is to duplicate my root include into each of my supported frameworks, so that only one buildOptions object specifies everything for a particular build.

Environment data

dotnet --info output:

.NET Command Line Tools (1.0.0-preview2-003093)

Product Information:
 Version:            1.0.0-preview2-003093
 Commit SHA-1 hash:  f4a8df3a56

Runtime Environment:
 OS Name:     ubuntu
 OS Version:  14.04
 OS Platform: Linux
 RID:         ubuntu.14.04-x64

/cc @ajaybhargavb

[ericstj]

@piotrpMSFT @blackdwarf this is a request to layer some/all build options between the generic set and the framework specific set. Can you please triage?

[brthor]

Added to tracking.