Disable the tests that verify that the available space shrunk

Somehow, it doesn't shrink with btrfs, even if you write 1 MB of non-
null data. This does not seem to be a bug in QStorageInfo. strace
confirms that there is a second statvfs call happening.

Change-Id: I9ed99d27d25e191916278e6b8faeae132469fc63
Reviewed-by: Oswald Buddenhagen <oswald.buddenhagen@theqtcompany.com>
Work around ICC compatibility problem with Apple headers

Apple uses __OSX_AVAILABLE_STARTING in enum values too, which ICC
doesn't like. We need to force at least OS X 10.9 so we don't run into
build errors.

FSEvents.h(279): error: expected a "}"
    kFSEventStreamCreateFlagMarkSelf __OSX_AVAILABLE_STARTING(__MAC_10_9, __IPHONE_7_0) = 0x00000020
                                     ^

Intel issue ID: 6000071924
Change-Id: Iae1abb8e8e92f228571c5064d96e9d33d3e35173
Reviewed-by: Oswald Buddenhagen <oswald.buddenhagen@theqtcompany.com>
Reviewed-by: Tor Arne Vestbø <tor.arne.vestbo@digia.com>
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>