Since High Sierra upgrade having a seperate line for platform_define 17 caused issues.
OTP 19 seemingly matched against it. OTP 18 had a redefine issue as it appeared to match against it as well.
Using this regex instead seems to work. Why? Why was htis not an issue before High Sierra?
this required a switch to change the sync strategy based on rebar parameter.
However tests could be slow on macbook with OTP16 and sync - so timeouts added in unit tests, and ct tests sync_startegy changed to not sync for OTP16.
