Add Alpine 3.21 #35

Job	Run time
build / build (alpine318)	5m 32s
build / build (alpine319)	6m 50s
build / build (alpine320)	6m 23s
build / build (alpine321)	10m 47s
build / build (debian12)	11m 15s
build / build (fedora41)	17m 37s
build / build (fedora40)	13m 59s
build / build (opensuseleap156)	22m 57s
build / build (opensusetumbleweed)	16m 43s
build / build (silverblue41)	21m 47s
build / build (silverblue40)	14m 3s
build / build (ubuntu2204)	21m 32s
build / build (ubuntu2404)	19m 17s
build / build (ubuntu2410)	18m 45s
	3h 27m 27s

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