llext: compile llext with arc mwdt on nsim vpx5

Allow users to compile LLEXTs with the MetaWare Design Toolchain.
Provides utility to dramatically shrink bloated extensions by removing
unused section names left behind by MWDT strip. Test extensions will
not fit in NSIM VPX5 memory otherwise; each is reduced from ~16k to ~1k.

Signed-off-by: Lauren Murphy <lauren.murphy@intel.com>