LLEXT: fix a needless allocation #146417

Job	Run time
twister-build-prep	2m 39s
twister-build (1)	31m 32s
twister-build (2)	29m 32s
twister-build (3)	29m 45s
twister-build (4)	35m 57s
twister-build (5)	24m 31s
twister-build (6)	22m 39s
twister-build (7)	33m 27s
Publish Unit Tests Results	21s
Check Twister Status / all jobs passed	1s
	3h 30m 24s

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