Each IDE has own rules. Segger studio of course doesn't support makefile and what it needs is in \modules\nrfx\mdk\ses_nrf52_startup.s about vectors, flash_placement_nrf52832.xml about memory layout and arm basic file "thumb_crt0_nrf52832.s"... It's a basic rule: If import a project to a new platform, the original part of build should give up and just remove the .c and .h. In RUI, the source should be removed and ignore build. In fact there are many amateurs have done similar work and post their achievement on nordic devzone, like:
and related video like:
If you post your issue on nordic devzone, they will give more professional advisement. When I build the gcc version, I take example by nordic example code. So I recommend you have a look at it like:\examples\ble_peripheral\ble_app_blinky\pca10040\s132\ses.