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.
using a GNU toolset in order to link with a library called libstm32f429i-disco_hal_lib (or for sempicity libMyLib) you have to pass the name of library without the prefix "lib". So in your case -lstm32f429i-disco_hal_lib (or -lMyLib).