Arduino Pro Mini name in CMakeList.txt in CLion
The problem here is that the Pro Mini comes in a number of variants for different voltages / speeds etc. The different variants are selected using a menu in the IDE.

CLion doesn't know about those menus, nor how to find the f_cpu from the right one for your board.

So there are two solutions:


Create your own board entry for the Pro Mini without the menu entries. 
Use an earlier version of the IDE that has the Pro Mini boards as separate entries (basically any version before the menu system was created).


If you want the latest API then you will have to go route 1. That could be as simple as modifying the existing pro.* entries to remove the menu and replace that section with just the flags that are set by the correct menu (basically remove all the pro.menu.* entries except the ones for your board, then remove the menu.cpu.&lt;whatever&gt;. from each of the lines, as well as the entire menu entry name line.)

So you would basically change these lines:

## Arduino Pro or Pro Mini (5V, 16 MHz) w/ ATmega328
## -------------------------------------------------
pro.menu.cpu.16MHzatmega328=ATmega328 (5V, 16 MHz)

pro.menu.cpu.16MHzatmega328.upload.maximum_size=30720
pro.menu.cpu.16MHzatmega328.upload.maximum_data_size=2048
pro.menu.cpu.16MHzatmega328.upload.speed=57600

pro.menu.cpu.16MHzatmega328.bootloader.low_fuses=0xFF
pro.menu.cpu.16MHzatmega328.bootloader.high_fuses=0xDA
pro.menu.cpu.16MHzatmega328.bootloader.extended_fuses=0x05
pro.menu.cpu.16MHzatmega328.bootloader.file=atmega/ATmegaBOOT_168_atmega328.hex

pro.menu.cpu.16MHzatmega328.build.mcu=atmega328p
pro.menu.cpu.16MHzatmega328.build.f_cpu=16000000L


to this:

## Arduino Pro or Pro Mini (5V, 16 MHz) w/ ATmega328
## -------------------------------------------------    
pro.upload.maximum_size=30720
pro.upload.maximum_data_size=2048
pro.upload.speed=57600

pro.bootloader.low_fuses=0xFF
pro.bootloader.high_fuses=0xDA
pro.bootloader.extended_fuses=0x05
pro.bootloader.file=atmega/ATmegaBOOT_168_atmega328.hex

pro.build.mcu=atmega328p
pro.build.f_cpu=16000000L


and delete all the other pro.menu entries.