Is it possible to build mac os client in the same was as windows cross compile in ubuntu?
Also building the latest source (windows client compiled in ubuntu) crashes with exception code exception code c0000005 which according to google is an access violation. Could this be the result of a bad compilation or something else ?
Can you give us some more information? config.log, shell dumps, etc.? In general, you can easily cross-compile OSX and windows binaries on ubuntu/linux. Check https://github.com/bitcoin/bitcoin/tree/master/depends
Also building the latest source (windows client compiled in ubuntu) crashes with exception code exception code c0000005 which according to google is an access violation
That's weird. I've built master for windows and tested it successfully for a while less than a week ago. I'm sure it can be caused by wrong compiler circumstances, but to troubleshoot this we need more information (as @jonasschnelli already says). Note that we use Ubuntu 14.04 for building the windows executable (both on travis as for the gitian release), older or newer mingw-w64 versions aren't regularly tested.
In general, you can easily cross-compile OSX and windows binaries on ubuntu/linux.
For information about OSX building see also:https://github.com/bitcoin/bitcoin/blob/master/doc/README_osx.md
Closing as no new information has been posted, and using the depends system was suggested.