Only add to preDeps when it's not in there.
depends: fix sed in libgcrypt which wants to change the optimisation but also might change other stuff we don't want (e.x. XBMC-OSX to XBMC-O1SX :p)
[osx] - adapt osx packaging - make it similar to what we do on ios and atv2 for consistency reasons
[osx/ios/atv2] - add XBMC_DEPENDS_ROOT and us it for constructing XBMC_DEPENDS - allows overwrite of XBMC_DEPENDS_ROOT when building with xcodebuild from commandline
[atv2/ios/osx] - add buildsteps for usage with jenkins