Merging r143686:

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r143686 | chandlerc | 2011-11-04 00:34:47 -0700 (Fri, 04 Nov 2011) | 4 lines

Sink the handling of -fobjc-arc-cxxlib to live with the other -fobjc-arc
implementation in the driver. This cleans up the signature and semantics
of the include flag adding component of the toolchain. Another step to
ready it for holding all the InitHeaderSearch logic.
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llvm-svn: 143927