Add support for RISC-V #1412

Job	Run time
build / Build	7m 1s
E2E Tests (startup)	8m 54s
E2E Tests (s3)	8m 33s
E2E Tests (btrfs)	4m 24s
E2E Tests (externalip)	5m 1s
Docker Tests (basics)	1m 4s
E2E Tests (privateregistry)	5m 32s
Docker Tests (bootstraptoken)	45s
E2E Tests (embeddedmirror)	5m 50s
Docker Tests (cacerts)	48s
E2E Tests (wasm)	3m 46s
Docker Tests (compat)	2m 30s
Docker Tests (lazypull)	50s
Docker Tests (upgrade)	2m 23s
	57m 21s

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