Move hooks into regular build chain

[hasselmm]

Currently hooks are run during the configure step.

This causes the following problems:

• it is conceptionally wrong
• hook artifacts are not rebuild after clean
• it wastes time during initial configuration (run four times via CMakeDeterminateSystem.cmake, CMakeSystem.cmake, CMakeDeterminateCCompiler.cmake, and CMakeDeterminateCXXCompiler.cmake)
• no idea how to run post hooks with that approach

Better plan: Setup custom commands that generate stamp files for each hook. These stamp files and all the build targets depend upon each other. Postlink hooks would be injected between the *.elf and the .bin target.

Ideally the script even runs CMake's GLOB_RECURSE after running hooks to properly update clean files.

[hasselmm]

Oh, the joy: The file {build.path}/sketch/requiredLibraries.cpp is needed at configure time already (#5), but it usually gets generated by hooks.