OSX Build broken past 2 months - could not find a valid SDK

 

OSX builds have been broken and not built the past 2 months...

https://travis-ci.org/OpenSmalltalk/opensmalltalk-vm/builds 

since commit "Update minimum SDK for 64-bit Mac to 10.12 (for metal)"...

https://github.com/OpenSmalltalk/opensmalltalk-vm/compare/191f9011b5e2...72506af6911a  

- #Build the oldest SDK installed (must be MacOSX10.11.sdk because of Metal and later)

+ #Build oldest installed SDK (must be MacOSX10.12.sdk because of Metal and later)

- SDKs:=MacOSX10.11.sdk MacOSX10.12.sdk MacOSX10.13.sdk MacOSX10.14.sdk

+ SDKs:=MacOSX10.12.sdk MacOSX10.13.sdk MacOSX10.14.sdk

The fix is potentially not difficult. Our travis.yml specifies...

     osx_image: xcode7.3

which at https://docs-staging.travis-ci.com/user/reference/osx#os-x-version

is shown to be OSX 10.11, which was just removed.

It seems we have four options: xcode9.2, xcode9.1, xcode9, xcode8.3.

Can someone with OSX experience please choose one and commit it for Travis to check?

This will facilitate correct results for CI testing of PRs. 

cheers -ben