System: ubuntu 18.04 Bitcoin version: 0.21

I successfully compiled the Ubuntu-qt, and Windows-qt using the Depends system. However, I am having a hard time doing the same for MacOSX using Ubuntu System.

I have downloaded the SDK from here :

https://developer.apple.com/devcenter/download.action?path=/Developer_Tools/Xcode_7.3.1/Xcode_7.3.1.dmg 

Extracted it using the script in contrib folder, then created a directory /depends/SDKs and place the extracted SDK in there.

After that, I run:

make HOST=x86_64-apple-darwin18 SDK_PATH=<some-path>/depends/SDKs/MacOSX10.11.sdk/ 

But everytime I end up with same error:

./boost/config/posix_features.hpp:18:15: fatal error: 'unistd.h' file not found funcs.mk:242: recipe for target 'path/depends/work/build/x86_64-apple-darwin18/boost/1_64_0-57fba19f366/./.stamp_built' failed 

Can you someone help ?