fix: ASMM files

[Maobuff]

This patch allows build STM32 projects that use threadx. (resolves #181)
There might be duplicates of ".S" files in STM32Make.make file inside ASM_SOURCES and ASMM_SOURCES variables.
Unfortunately, it breaks the ability for an extension to auto-search for assembly language files(".S").
However, I don't think that assembly should be autosearched anyway.

[jortbmd]

Hi thanks so much for creating a pull request! I would prefer to keep the searching of assembly files in there. I incidentally also started working on this. I have a beta version of this out right now. Will test it a bit an maybe add some extra features I have been promising but it should work for your case.
You can find it here: https://github.com/bmd-studio/stm32-for-vscode/releases/tag/v3.2.7-beta
Could you check if this works for you? You can install it by downloading the VSIX package and then use ctrl/CMD+shift+p and selecting Extensions: Install from VSIX.
Hoping to release a new minor version soon which should fix this for you. Will update you once I have done this.

[Maobuff]

I can confirm that firmware is building. I will test output firmware on actual hardware later just to be sure.