Here below an example of how to use CMake to build assembly language programs. The example below assumes you've got a hello.asm in the directory src/asm/ of your project directory.

hello.asm

;name: hello.asm
;
;description: example of a build with cmake and nasm
;
;build:
;    in the project root directory
;    cmake .
;    make

global  _start

section .data
msg     db      'Hello world', 0x0A
.len    equ     $ - msg

section .text

_start:
    xor     rax,rax
    inc     rax             ;syscall for write
    mov     rdi,rax         ;stdout also 1
    mov     rsi,msg         ;address of the message
    mov     rdx,msg.len     ;length of the message
    syscall
    mov     rax,60          ;syscall for exit
    xor     rdi,rdi         ;return 0
    syscall

The CMakeList.txt must be in the root directory of your project. 

CMakeLists.txt

cmake_minimum_required(VERSION 3.7)

set(CMAKE_VERBOSE_MAKEFILE ON)

set(project_name "hello")

set(CMAKE_NASM_LINK_EXECUTABLE "ld   -o  ")
set(CAN_USE_ASSEMBLER TRUE)

set(CMAKE_ASM_NASM_FLAGS "")
set(CMAKE_EXE_LINKER_FLAGS "${CMAKE_EXE_LINKER_FLAGS}")

set(CMAKE_ASM_NASM_OBJECT_FORMAT elf64)

project(${project_name} ASM_NASM)

enable_language(ASM_NASM)
set(SOURCE_FILES src/asm/hello.asm)

add_executable(${project_name} ${SOURCE_FILES})
set_target_properties(${project_name} PROPERTIES LINKER_LANGUAGE NASM)

If all went well you should have a construction like in the image

Building the example is fairly simple, just run in your root directory (you can make a shell script if you like to build it from GUI. So open a terminal (CTRL-ALT-T) and run:

cmake .
make

Your project directory should look similar to

running ./hello will show you the message on screen.

https://gitlab.kitware.com/cmake/community/-/wikis/doc/cmake/languages/Assembler