llext: add vsnprintf to exported symbols #790

Job	Run time
Build and package cores	8m 55s
Split off zephyr_unoq	15s
Split off zephyr_contrib	14s
Split off zephyr_main	8s
Split off zephyr	12s
Test zephyr_main:opta	2m 33s
Test zephyr_main:giga	2m 32s
Test zephyr_contrib:ek_ra8d1	2m 23s
Test zephyr_main:portentac33	2m 28s
Test zephyr_contrib:frdm_mcxn947	2m 22s
Test zephyr_main:nano33ble	2m 26s
Test zephyr_main:portentah7	2m 34s
Test zephyr_main:niclasense	2m 25s
Test zephyr_contrib:frdm_rw612	2m 19s
Test zephyr:unoq	2m 19s
Publish core	27s
Collect logs	8s
Publish jsons	22s
verify-core	0s
cleanup-artifacts	3s
	35m 5s

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