add a makefile for all example project (board_examples/CMakeLists.txt)
remove non working examples (sdcard and sandbox)
compile example with embedded library (still experimental)
link with whole-archive flags

we must force the linker to consider all the modules contained in the static library.
If we do not use this flag, the linker does not include static constructors (for the clock) and the Reset_Handler
Merge branch 'compile_all'

Conflicts:
	backends/cmake/copy_hal_files_helper.cmake