Avoid some redundant downloads

Makefile

@@ -8,20 +8,20 @@ test:
 	@echo ok
 
 .PHONY: build
-build:
+build: build/qemu-x86_64-static
 	docker build . -t ${DOCKER_TAG}
 
 build/qemu-arm-static:
-	./get_qemu.sh
+	./get_qemu2.sh arm
 
 build/qemu-x86_64-static:
-	./get_qemu.sh
+	./get_qemu2.sh x86_64
 
 build/qemu-aarch64-static:
-	./get_qemu.sh
+	./get_qemu2.sh aarch64
 
 .PHONY: cross-build-arm
-cross-build-arm:
+cross-build-arm: build/qemu-arm-static
 	docker build --build-arg REPO=arm32v6 --build-arg ARCH=arm . -t ${DOCKER_TAG}-arm32v6
 
 .PHONY: run

get_qemu2.sh

@@ -10,5 +10,4 @@ for target_arch in $*; do
   wget -N https://github.com/multiarch/qemu-user-static/releases/download/$VERSION/${HOST_ARCH}_qemu-${target_arch}-static.tar.gz
   tar -xvf ${HOST_ARCH}_qemu-${target_arch}-static.tar.gz
   rm ${HOST_ARCH}_qemu-${target_arch}-static.tar.gz
-  mv qemu-${target_arch}-static /usr/bin/
 done