[CMake] Enhance mma and mm function by removing CMakeCache.txt file

As we are using multiple compiler, we sometimes have to run mmc before
mma or mm because CMake remember the last compiler used.
This patch removes the CMakeCache.txt file before running cmake.

Signed-off-by: clero <clero@etud.insa-toulouse.fr>
[CMake] Add ability to use HF arm compiler

This patch introduce the TARGETSOFTFP value for BUILD_DESTINATION cmake option.
This option allows to use soft fp compiler instead of an HF one.
All subdirectories which have to be built with a softfp compiler have to
be added to the target_softfp_projects.cmake file.

Signed-off-by: clero <clero@etud.insa-toulouse.fr>