Support building casync on macOS

[makeamark1]

Would it please be possible to supporting building casync on macOS too? What, if any, would the major hurdles be to support building on macOS?

[elfgoh]

@markhalm256 have you tried? What issues have you ran into?

[makeamark1]

@elfgoh I have not tried it myself yet.

[aleivag]

@markhallm i think what its going to be the hardest about porting is the dependency of linux libraries like

https://github.com/systemd/casync/blob/master/src/util.h#L20-L23

dont know if those are available under macos

[makeamark1]

By the way, the desync project might be an alternative on macOS: "Supported on MacOS, though there could be incompatibilities when exchanging catar-files between Linux and Mac for example since devices and filemodes differ slightly."

[rossburton]

I just tried building it, first failure was no libacl available.