Support parallel builds with make (#491) #35

Job	Run time
build-native-gcc	3m 15s
build-native-llvm	3m 52s
test-native-gcc	7m 54s
build-aarch64-gcc	7m 44s
test-native-llvm	7m 11s
build-aarch64-llvm	7m 1s
build-armhf-gcc	1m 38s
build-armhf-llvm	1m 49s
build-ppc64el-gcc	4m 10s
build-ppc64el-llvm	2m 54s
build-s390x-gcc	2m 21s
build-s390x-llvm	3m 31s
build-riscv64-llvm	2m 3s
test-aarch64-gcc (qemu_cpu: "max,sve=off")	21m 1s
test-aarch64-gcc (qemu_cpu: "max,sve=on,sve128=on")	22m 53s
test-aarch64-gcc (qemu_cpu: "max,sve=on,sve256=on")	29m 59s
test-aarch64-gcc (qemu_cpu: "max,sve=on,sve512=on")	32m 26s
test-armhf-gcc (qemu_cpu: "max")	14m 20s
test-armhf-llvm (qemu_cpu: "max")	13m 32s
test-ppc64el-gcc (qemu_cpu: "power10")	28m 3s
test-ppc64el-llvm (qemu_cpu: "power10")	27m 51s
test-s390x-gcc (qemu_cpu: "")	22m 50s
test-s390x-llvm (qemu_cpu: "")	18m 29s
test-riscv64-llvm (qemu_cpu: "rv64,zba=true,zbb=true,zbs=true,v=false")	7m 20s
test-riscv64-llvm (qemu_cpu: "rv64,zba=true,zbb=true,zbs=true,v=true,vlen=128,elen=64,vext_spec=v1.0")	13m 58s
test-riscv64-llvm (qemu_cpu: "rv64,zba=true,zbb=true,zbs=true,v=true,vlen=256,elen=64,vext_spec=v1.0")	22m 12s
test-riscv64-llvm (qemu_cpu: "rv64,zba=true,zbb=true,zbs=true,v=true,vlen=512,elen=64,vext_spec=v1.0")	34m 16s
	6h 4m 33s

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