iosbuild.sh: portable sed usage
iosbuild.sh: portable sed usage

There is no convenient way to have both gnu and bsd
sed do in-place processing.

Change-Id: I95f2a378d5c1bd95debb446317cc18ad79835e49

webmproject/libvpx,ShiftMediaProject/libvpx,ShiftMediaProject/libvpx,webmproject/libvpx,webmproject/libvpx,ShiftMediaProject/libvpx,webmproject/libvpx,ShiftMediaProject/libvpx,webmproject/libvpx,webmproject/libvpx,ShiftMediaProject/libvpx