Changes since v0.5.0:
* Add spec files for am64x SoCs.
* Require Binutils at least version 2.37.
* Require pru-gcc to be installed.
* Remove linker scripts. Instead set memory sizes from specs.
* Activate --gc-sections linker option by default.
* The "--host=pru" configure option must be used instead of "--target=pru.
Signed-off-by: Dimitar Dimitrov <dimitar@dinux.eu>