Cortex-M7 Toolchain & STM32 Skeleton

[alieissa-commits]

Description

Establish the CMake toolchain for the Cortex-M7 and write the low-level initialization code for the STM32F767ZI-Nucleo-144.

• Create the cmake/arm-gcc-cortex-m7.cmake file and configure it to inherit from the generic toolchain.
• Create the src/STMicroelectronics/STM32F767ZI-Nucleo/ directory structure.
• Implement the startup/ files, including the linker script and vendor vector table.
• Draft board_init.c to configure the SystemClock at 216 MHz.
• Initialize the LAN8742A Ethernet PHY.