errors for run-tests were sometimes being swallowed.

e.g., if the test bundle didn't generate correctly, the output looked
like...

```
  run-test TestProject-LibraryTests.octest (iphonesimulator6.1, logic-test, GC OFF)

** TEST FAILED: 0 of 0 tests passed ** (1167 ms)
```

We had a check that said if the tests failed to run && we got no test
events, pretend things succeeded.  This was to immitate some Xcode
behavior.  But, really, we should only do that when we don't have an
error message.

Now output looks like...

```
  run-test TestProject-LibraryTests.octest (iphonesimulator6.1, logic-test, GC OFF)
  failed: Test bundle not found at:
/Users/fpotter/Library/Developer/Xcode/DerivedData/TestProject-Library-gqcuxcsyguaqwugnnwmftlazxbyg/Build/Products/Release-iphonesimulator/TestProject-LibraryTests.octest
** TEST FAILED: 0 of 0 tests passed ** (1167 ms)
```
a simple test for the 'archive' action.

Just make sure xcodebuild gets invoked with 'archive'
compensate for xcodebuild bug where 'archive' always claims to succeed

xcodebuild's archive action always claims to succeed (with exit status
of 0) even when there are failing build commands.

To compensate, we only claim xcodebuild succeeds when we see no failing
build commands from xcodebuild.