llext: add vsnprintf to exported symbols #791

Job	Run time
Build and package cores	9m 15s
Split off zephyr	8s
Split off zephyr_contrib	13s
Split off zephyr_main	14s
Split off zephyr_unoq	14s
Test zephyr_main:nano33ble	2m 23s
Test zephyr_main:niclasense	1m 54s
Test zephyr_contrib:ek_ra8d1	2m 23s
Test zephyr_main:giga	2m 31s
Test zephyr_main:portentac33	2m 26s
Test zephyr:unoq	2m 20s
Test zephyr_main:opta	2m 27s
Test zephyr_main:portentah7	2m 25s
Test zephyr_contrib:frdm_rw612	2m 18s
Test zephyr_contrib:frdm_mcxn947	2m 21s
Collect logs	9s
Publish jsons	16s
Publish core	-1s
verify-core	-1s
cleanup-artifacts	3s
	33m 58s

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