EmbeddedPkg/FdtLib: build fdt_empty_tree.c
EmbeddedPkg/FdtLib: build fdt_empty_tree.c

We're currently building everything except for this file.
Since 'fdt_create_empty_tree' can be useful for some
platforms, compile this one too.

Contributed-under: TianoCore Contribution Agreement 1.1
Signed-off-by: Michael Zimmermann <13027ca0fefa2b406bb0e61c3b36bc21411fbb83@gmail.com>
Reviewed-by: Ard Biesheuvel <66d3c5fdaeea7ff1f996ad04f2c45e08ab38e2f5@linaro.org>

MattDevo/edk2,MattDevo/edk2,MattDevo/edk2,MattDevo/edk2,MattDevo/edk2,MattDevo/edk2,MattDevo/edk2,MattDevo/edk2