Integrate RISC-V support #2

Job	Run time
build-native	7m 33s
test-native	14m 55s
build-aarch64	3m 10s
build-armhf	1m 11s
build-ppc64el	4m 56s
build-s390x	2m 16s
build-riscv64	4m 43s
test-aarch64 (qemu_cpu: "max,sve=off")	17m 17s
test-aarch64 (qemu_cpu: "max,sve=on,sve128=on")	16m 49s
test-aarch64 (qemu_cpu: "max,sve=on,sve256=on")	17m 16s
test-aarch64 (qemu_cpu: "max,sve=on,sve512=on")	19m 58s
test-armhf (qemu_cpu: "max")	6m 40s
test-ppc64el (qemu_cpu: "power10")	20m 35s
test-s390x (qemu_cpu: "")	13m 19s
test-riscv64 (qemu_cpu: "rv64,zba=true,zbb=true,zbs=true,v=false")	4m 29s
test-riscv64 (qemu_cpu: "rv64,zba=true,zbb=true,zbs=true,v=true,vlen=128,elen=64,vext_spec=v1.0")	8m 26s
test-riscv64 (qemu_cpu: "rv64,zba=true,zbb=true,zbs=true,v=true,vlen=256,elen=64,vext_spec=v1.0")	7m 57s
test-riscv64 (qemu_cpu: "rv64,zba=true,zbb=true,zbs=true,v=true,vlen=512,elen=64,vext_spec=v1.0")	12m 29s
	3h 3m 59s

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