llext: add initial support for arc #146334

Job	Run time
twister-build-prep	3m 30s
twister-build (1)	38m 33s
twister-build (2)	30m 25s
twister-build (3)	45m 6s
twister-build (4)	24m 43s
twister-build (5)	32m 35s
twister-build (6)	1h 8m 24s
twister-build (7)	58m 9s
twister-build (8)	39m 16s
twister-build (9)	29m 17s
twister-build (10)	20m 17s
twister-build (11)	35m 24s
twister-build (12)	33m 37s
twister-build (13)	33m 55s
twister-build (14)	32m 16s
twister-build (15)	30m 49s
Publish Unit Tests Results	26s
Check Twister Status / all jobs passed	1s
	9h 16m 43s

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