Build SDK repository.

When the build is invoked with the fake target "sdk_repo" and
a main target of sdk, win_sdk or sdk_addon, we now create
packages in DIST_DIR that can directly be used to populate the
SDK Repository.
This is quite close to how we actually distribute the SDK.

Change-Id: I01c729eff4dbc1eccbc7c5b1869f329363f1ce07
2 files changed