"flat varying" variables don't get parsed correctly into shaders

Summary: Flat variables don't get parsed correctly

Parsed shaders can be output by setting the 
QT_RHI_SHADER_DEBUG=1 runtime
flag!

Input

flat varying out vec4 myVar1;
varying flat out vec4 myVar2;

Current Output after compilation

layout(location=7) out vec4 myVar1;
layout(location=8) out vec4 myVar2;
flat
flat

Expected Output after compilation

layout(location=7) flat out vec4 myVar1; 
layout(location=8) flat out vec4 myVar2;

Notes: 
Code and output written from memory. I did not confirm if the issue affects both IN and OUT variables.