Universe: fix alpine.#Build

Signed-off-by: Sam Alba <samalba@users.noreply.github.com>

pkg/universe.dagger.io/alpine/alpine.cue

@@ -22,14 +22,16 @@ let defaultVersion = "3.13.5@sha256:69e70a79f2d41ab5d637de98c1e0b055206ba40a8145
 				source: "index.docker.io/alpine:\(version)"
 			},
 			for pkgName, pkg in packages {
-				run: cmd: {
+				docker.#Run & {
+					cmd: {
 						name: "apk"
-					args: ["add", "\(pkgName)\(version)"]
+						args: ["add", "\(pkgName)\(pkg.version)"]
 						flags: {
 							"-U":         true
 							"--no-cache": true
 						}
 					}
+				}
 			},
 		]
 	}

pkg/universe.dagger.io/yarn/yarn.cue

@@ -47,9 +47,13 @@ import (
 	// Yarn version
 	// yarnVersion: *"=~1.22" | string
 
-	// FIXME: trouble getting docker.#Build to work (cueflow task dependencies not working)
-	image: alpine.#Build & {
-		packages: "bash": {}
+	image: docker.#Image | *{
+		alpine.#Build & {
+		packages: {
+			"bash": {}
+			"yarn": {}
+		}
+	}
 	}
 
 	// Run yarn in a containerized build environment