This allows building two versions for different architectures at
the same time, without the built files clobbering each other.
This is very helpful when trying to track down differences between
two build configurations.
To build outside of the source tree, create the other directory to
use for building (either outside of the openh264 directory, or as
a subdirectory), enter that directory, and do
"make -f path/to/openh264/Makefile".
This avoids having to update the makefile just to change the SDK
version whenever the iOS SDK is updated (since the previous
version is removed on updates).
This doesn't build the actual demo apps that you can run on the
phone (not yet at least), but is useful for easily testing compilation
in different setups, and for building a precompiled static library for
use in external projects.
