Arm64 build

[hreuver0183]

Patch cmake:
cmake sees ARM and builds a package for ARMHF.
for ARM64 this will not work, therefore copy some checks from OpenCPN to build for ARM64.

Fix for #52

Patch oesenc_pi.cpp:
SGlock is not supported for ARM64, the oeserverd for ARM64 is older than for other platforms.
Some commandline options are missing from the ARM64-version.
Those commandline options break oesenc_pi.

With one IFDEF the faulty check is bypassed, allowing for oesenc_pi to work with FPR.
With the system FPR using o-charts with ARM64 is again possible.
(Actually 2 IFDEF's, the other prevents creating a USB key dongle System ID file and is already present in the code.)

Fix for #56
Partial fix for issue #55, since SGlock still does not work.

[rgleason]

If this is accepted and works properly, my repos ci branch should be changed too, so that other pi benefit.

[rgleason]

Dave should I make these changes?

[bdbcat]

Yes.