Development tools for Zephyr on STM32Workbench for Zephyr: VS Code extension to set up, build, flash and debug Zephyr applications on STM32.Devicetree manager: browse, edit and visualize Zephyr devicetree, STM32CubeMX-like for Zephyr.
You need either to add syscall.c to your project or add "-specs=nosys.specs" to (Project -> Properties -> C/C++ Build -> Settings -> MCU GCC Linker -> Linker flags)