Core apparently doesn't build on Windows/OSX

[tomaka]

Because of linking issues with emit_message, cancel_message, etc.

The problem is that the core depends on a bunch of crates which in turn depend on syscalls-interface, which has these functions as extern functions.

This needs a lot of unclear refactoring.

[gustavolsson]

I get the following error when trying to build hello-world on OSX 10.15.2 as well:

  = note: Undefined symbols for architecture x86_64:
            "_emit_message", referenced from:
                redshirt_syscalls_interface::emit::MessageBuilder$LT$TLen$GT$::emit_raw::h6a473b1490af9c68 in libredshirt_stdout_interface-058555e5f4063c36.rlib(redshirt_stdout_interface-058555e5f4063c36.246sb9gtq03wi8ah.rcgu.o)
          ld: symbol(s) not found for architecture x86_64
          clang: error: linker command failed with exit code 1 (use -v to see invocation)
          

error: aborting due to previous error

error: could not compile `hello-world`.