ios: remove linking of qiosmain as it isn't needed anymore

Task-number: QBS-347
Change-Id: Ifd390ad0aa89384c6269b7641eb3f89124e9c066
Reviewed-by: Joerg Bornemann <joerg.bornemann@digia.com>
Improve JS extension class "Process".

- Get rid of irrelevant functionality.
- Add ability to retrieve stderr output and exit code.
- Make it possible to tell a process to throw a JS exception
  on failure.
- Use above feature in DarwinGCC.qbs. This will make problems such
  as QBS-348 easier to diagnose in the future.
- Remove nonsensical checks and conversions.

Change-Id: Ie823a21c2cb86c66269c120069cf1d2022d9aa05
Reviewed-by: Joerg Bornemann <joerg.bornemann@digia.com>
Make the Loader print progress information also in BuildGraphLoader.

Otherwise, a certain amount of time passes without any progress
information in the case that a project needs to be re-resolved after
restoring.

Change-Id: I15e4e8cdece43a93c6be028c621aba844be5e01c
Reviewed-by: Joerg Bornemann <joerg.bornemann@digia.com>
Make the qbs project files embeddable in another project.

The qmake project files already have this ability.

Change-Id: I9d01609525b410a7cf0bb86865aa85c5435bad03
Reviewed-by: Joerg Bornemann <joerg.bornemann@digia.com>