Xcode: Fix test architecture selection for Xcode >= 5

In Tests/Architecture and Tests/BuildDepends/Project we select a set of
OS X cpu architectures to use for the test.  Prior to Xcode 4 we always
used i386 and ppc.  Starting with Xcode 4, the tools do not support ppc
but do support x86_64, so we switch to that.  Fix the version check to
recognize Xcode >= 5 as at least Xcode 4 and use the new architectures.
Xcode: Teach Tests/BuildDepends to allow LINK_DEPENDS_NO_SHARED failure

Xcode 5.0 now relinks targets when their shared libraries dependencies
are modified, and there seems to be no way to stop it.  Report this as a
known limitation in the test output and do not fail.
Xcode: Drop XCODE_DEPEND_HELPER for Xcode >= 5

Xcode 5.0 now computes dependencies from files linked through
OTHER_LDFLAGS, so we no longer need the XCODE_DEPEND_HELPER hack to
re-link dependents when targets change.
Xcode: Fix OBJECT library support for Xcode 5 (#14254)

Xcode 2.1 through 4 supported $(CURRENT_ARCH) in a PBXFileReference
'path' value used in the "Link Binary with Libraries" build phase.
CMake uses this to reference object file locations on link lines to
bring in OBJECT library content.  However, Xcode 5 now evaluates the
$(CURRENT_ARCH) reference in this context as "undefined_arch" so the
wrong path is given to the linker.  There seems to be no alternative way
to produce an architecture-specific value in a PBXFileReference.

Fortunately Xcode 5 now also handles link dependencies for paths linked
through OTHER_LDFLAGS.  For Xcode >= 5, move the OBJECT library object
file references from the link build phase to OTHER_LDFLAGS.  We can
still show the object files in the source group listing in either case.
Merge topic 'xcode-5'

a3194ff Xcode: Fix OBJECT library support for Xcode 5 (#14254)
dff8d11 Xcode: Drop XCODE_DEPEND_HELPER for Xcode >= 5
1180322 Xcode: Teach Tests/BuildDepends to allow LINK_DEPENDS_NO_SHARED failure
765b46d Xcode: Fix test architecture selection for Xcode >= 5