i would like to use the QN9090 with the VisualGDB IDE, for this I need to import the GCC toolchain. NXP does not provide this toolchain. Only MCUXpresso IDE and IAR Embedded Workbench for ARM.
How can I still use this MCU with VisualGDB?
You can try following this tutorial to setup the project manually. Also, if IAR supports the device out-of-the-box, you can the IAR compiler with VisualGDB as shown here.
We can also do the necessary research and build the BSP for you for a small fee if you prefer.