How to add Assebly files to Qt project?

[Zingam]

I would like to use x86 and ARM assembly in my Qt projects.
What would be the recommened way to add external files in assembly to Qt Creator?

I tried to add a file to the project:

QT       += core gui
 
greaterThan(QT_MAJOR_VERSION, 4): QT += widgets
 
TARGET = ImageManipulator
TEMPLATE = app
 
QMAKE_CXXFLAGS +=-masm=intel
 
SOURCES += main.cpp\
        mainwindow.cpp\
        functions.s
 
HEADERS  += mainwindow.h
 
FORMS    += mainwindow.ui

QT       += core gui

greaterThan(QT_MAJOR_VERSION, 4): QT += widgets

TARGET = ImageManipulator
TEMPLATE = app

QMAKE_CXXFLAGS +=-masm=intel

SOURCES += main.cpp\
        mainwindow.cpp\
        functions.s

HEADERS  += mainwindow.h

FORMS    += mainwindow.ui

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function.s gets compiled to .o but the linker cannot find the functions.

Also if I use QMAKE_CXXFLAGS += -masm=intel
This causes:
{standard input}: Assembler messages:
{standard input}:1697: Error: no such instruction: `subl $1,DWORD PTR [eax]'
Even if there is no assebly at all.