Add RVV inline header support. #249

Job	Run time
build-native-gcc	3m 49s
build-native-llvm	4m 16s
test-native-gcc	9m 26s
build-aarch64-gcc	5m 50s
test-native-llvm	7m 28s
build-aarch64-llvm	5m 10s
build-armhf-gcc	6m 20s
build-armhf-llvm	3m 34s
build-ppc64el-gcc	9m 10s
build-ppc64el-llvm	6m 19s
build-s390x-gcc	5m 7s
build-s390x-llvm	6m 42s
build-riscv64-llvm	8m 23s
test-aarch64-gcc (qemu_cpu: "max,sve=off")	16m 35s
test-aarch64-gcc (qemu_cpu: "max,sve=on,sve128=on")	21m 35s
test-aarch64-gcc (qemu_cpu: "max,sve=on,sve256=on")	25m 22s
test-aarch64-gcc (qemu_cpu: "max,sve=on,sve512=on")	29m 17s
test-aarch64-llvm (qemu_cpu: "max,sve=off")	20m 12s
test-aarch64-llvm (qemu_cpu: "max,sve=on,sve128=on")	21m 34s
test-aarch64-llvm (qemu_cpu: "max,sve=on,sve256=on")	25m 24s
test-aarch64-llvm (qemu_cpu: "max,sve=on,sve512=on")	30m 13s
test-armhf-gcc (qemu_cpu: "max")	14m 45s
test-armhf-llvm (qemu_cpu: "max")	13m 33s
test-ppc64el-gcc (qemu_cpu: "power10")	29m 46s
test-ppc64el-llvm (qemu_cpu: "power10")	27m 56s
test-s390x-gcc (qemu_cpu: "")	19m 41s
test-s390x-llvm (qemu_cpu: "")	18m 51s
test-riscv64-llvm (qemu_cpu: "rv64,zba=true,zbb=true,zbs=true,v=false")	12m 44s
test-riscv64-llvm (qemu_cpu: "rv64,zba=true,zbb=true,zbs=true,v=true,vlen=128,elen=64,vext_spec=v1.0")	34m 12s
test-riscv64-llvm (qemu_cpu: "rv64,zba=true,zbb=true,zbs=true,v=true,vlen=256,elen=64,vext_spec=v1.0")	41m 15s
test-riscv64-llvm (qemu_cpu: "rv64,zba=true,zbb=true,zbs=true,v=true,vlen=512,elen=64,vext_spec=v1.0")	1h 3m 15s
	9h 7m 44s

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