Slow build
I found the build logging checkbox and disabled it but still no help. And i googled and googled again.
But as final desperate move i uninstalled the Bitdefender antivirus and voila - build time went from 3 minutes down to 9 seconds 😊
So i am going to write them a long letter....
Edit:
After some guiding from Bitdefender i added the c:\ac6\systemworkbench\plugins\fr.ac6.mcu.externaltools.arm-none.win32_1.13.2.201705091103\tools folder to "on-access" and "on-demand" scan exclusion list and that solved the issue.