Platform/DeveloperBox: conditionally include the X64 PE/COFF emulator
Add the X64 emulator to the build if '-D X64EMU_ENABLE=TRUE' is passed
on the build command line. Note that this only works on AARCH64 builds.
Contributed-under: TianoCore Contribution Agreement 1.1
Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Reviewed-by: Leif Lindholm <leif.lindholm@linaro.org>