iOS patch libraries/dph can't be omitted from the build on non-TH-capable platforms any more

We can't build without libraries/dph any more. This happens if we use ./sync-all --no-dph get, and it's needed on build configurations that don't support TH (such as cross-compiling).

I think this is a regression in the recent fix

commit 104ff6e9ad85751dab2fc2ed25cf8f7827bb13f1
Author: Ian Lynagh <ian@well-typed.com>
Date:   Fri Mar 1 16:34:33 2013 +0000

    Change how the build system handles packages
    
    This makes the build system a little simpler, and in particular
    will make it easier to handle the changes needed for cross-compilation.

Here's the output:

===--- building phase 0
... snip ...
ghc.mk:675: libraries/dph/ghc.mk: No such file or directory
make[1]: *** No rule to make target `libraries/dph/ghc.mk'.  Stop.

Trac metadata

Trac field	Value
Version	7.7
Type	Bug
TypeOfFailure	OtherFailure
Priority	normal
Resolution	Unresolved
Component	Build System
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