* add custom linker script
a custom linker script can be applied by adding the .ld filepath
as 2nd argument to mbed_set_post_build
* more detailed comment
* add if is_standalone for text cases
* replace COMMENT in add_custom_command by echo
COMMENT is not reliable printed
* First attempt at converting to OBJECT libraries. Not working due to more object library limitations
* Only compile the main libraries as OBJECT, because that's all that CMake can be made to do right now.
* Fix availability of target-specific flags
* Missed some usages
* Fix some STM32 ethernet stuff that was not linking correctly
* More fixes for STM32 ethernet and weak symbols
* Fix prebuilt object file linking for MUSCA_S1
* Fix STM32 eth init license headers
Jamie Smith
JojoS