add conditional compilation to build on OSX

Yeah.

> On 10 Nov 2014, at 08:03, yallop <notifications@github.com> wrote:
> 
> In remote-call-example/Makefile:
> 
> >  OCAML_LDFLAGS=$(LDFLAGS:%=-cclib %)
> > +OSR=$(shell uname -r)
> Ok to lose the -r here?
> 
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