Integrate RISC-V support #16

Job	Run time
build-native-gcc	5m 14s
build-native-llvm	5m 33s
test-native-gcc	7m 51s
test-native-llvm	8m 57s
build-aarch64-gcc	4m 35s
build-aarch64-llvm	2m 50s
build-armhf-gcc	3m 23s
build-armhf-llvm	3m 54s
build-ppc64el-gcc	2m 9s
build-ppc64el-llvm	5m 47s
build-s390x-gcc	1m 41s
build-s390x-llvm	3m 11s
build-riscv64-llvm	3m 53s
test-aarch64-gcc (qemu_cpu: "max,sve=off")	15m 23s
test-aarch64-gcc (qemu_cpu: "max,sve=on,sve128=on")	18m 33s
test-aarch64-gcc (qemu_cpu: "max,sve=on,sve256=on")	17m 36s
test-aarch64-gcc (qemu_cpu: "max,sve=on,sve512=on")	19m 20s
test-armhf-gcc (qemu_cpu: "max")	9m 13s
test-armhf-llvm (qemu_cpu: "max")	7m 43s
test-ppc64el-gcc (qemu_cpu: "power10")	17m 42s
test-ppc64el-llvm (qemu_cpu: "power10")	16m 16s
test-s390x-gcc (qemu_cpu: "")	16m 57s
test-s390x-llvm (qemu_cpu: "")	11m 50s
test-riscv64-llvm (qemu_cpu: "rv64,zba=true,zbb=true,zbs=true,v=false")	6m 36s
test-riscv64-llvm (qemu_cpu: "rv64,zba=true,zbb=true,zbs=true,v=true,vlen=128,elen=64,vext_spec=v1.0")	9m 10s
test-riscv64-llvm (qemu_cpu: "rv64,zba=true,zbb=true,zbs=true,v=true,vlen=256,elen=64,vext_spec=v1.0")	9m 18s
test-riscv64-llvm (qemu_cpu: "rv64,zba=true,zbb=true,zbs=true,v=true,vlen=512,elen=64,vext_spec=v1.0")	9m 17s
	4h 3m 52s

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