It is possible to have some files that build in the system environment
and some in the U-Boot environment. To build for the system, the system
headers must be used, or at least have priority. For a U-Boot file, its
headers must be used exclusively.
Expand the Makefile example to have two files, one of which is built
using U-Boot headers. This shows how a program can be built which
straddles both domains.
Signed-off-by: Simon Glass <sjg@chromium.org>
4c32ae1087