cli: enforce build for linux/riscv64 platform (#73)

* feat(cli): enforce build for linux/riscv64 platform

since the target is always a Cartesi Machine (riscv64), cartesi build
should enforce the docker build environment via --platform argument

.changeset/big-ghosts-rescue.md

@@ -0,0 +1,5 @@
+---
+"@cartesi/cli": patch
+---
+
+enforce build for linux/riscv64 platform

apps/cli/src/builder/docker.ts

@@ -26,6 +26,8 @@ const buildImage = async (options: ImageBuildOptions): Promise<string> => {
     const args = [
         "buildx",
         "build",
+        "--platform",
+        "linux/riscv64",
         "--file",
         dockerfile,
         "--load",
@@ -89,7 +91,13 @@ export const build = async (
     const filename = `${name}.${format}`;
 
     // use pre-existing image or build docker image
-    const image = drive.image || (await buildImage(drive));
+    let image: string;
+    if (drive.image) {
+        image = drive.image;
+        await execa("docker", ["image", "pull", image]);
+    } else {
+        image = await buildImage(drive);
+    }
 
     // get image info
     const imageInfo = await getImageInfo(image);

apps/cli/test/builder/docker.test.ts

@@ -35,11 +35,10 @@ describe("when building with the docker builder", () => {
         const drive: DockerDriveConfig = {
             builder: "docker",
             context: path.join(__dirname, "data"),
-            dockerfile: path.join(__dirname, "data", "Dockerfile.nonriscv"),
             extraSize: 0,
             format: "ext2",
             tags: [],
-            image: undefined,
+            image: "debian:bookworm-slim",
             target: undefined,
         };
         await expect(build("root", drive, image, destination)).rejects.toThrow(