GCC compiler version specified in kit is ignored by qmake

On my Linux system I have multiple versions of gcc, hence I created several kits to choose which one to use to compile.

When building a qmake project the compiler chosen in the active kit is always ignored and the default gcc compiler is used.

According to the Qt Creator manual:

In the Compiler field, select the C or C++ compiler used to build the project.

Which means that the kit is supposed to set the active compiler for the build.

The right compiler is chosen when I use a kit based on Clang.

Furthermore, everything is fine when the project is based on Qbs or CMake.

Steps to reproduce

A Linux system with multiple versions of gcc installed is required

1. Create a kit for each version of gcc
2. Create a Qt Console Application project and choose qmake as build system
3. Copy the main.cpp attached in this report
4. Build the project using a kit which is not based on the default compiler (for example gcc 5.5.0 in my case)
5. Run the project and verify that the compiler used is always the default one (8.2.0 in my case)