ci: cleaner pattern for sharing base images across actions

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

ci/main.cue

@@ -24,8 +24,8 @@ engine.#Plan & {
 	}
 
 	outputs: directories: "go binaries": {
-	 contents: actions.build.export.directories["/build"].contents
-	 dest:     "./build"
+		contents: actions.build.export.directories["/build"].contents
+		dest:     "./build"
 	}
 
 	actions: {
@@ -33,6 +33,8 @@ engine.#Plan & {
 			id: "go mod cache"
 		}
 
+		baseImages: #Images
+
 		source: "dagger source code": {
 			contents: inputs.directories.source.contents
 			dest:     "/usr/src/dagger"
@@ -40,7 +42,7 @@ engine.#Plan & {
 
 		// FIXME: build only if the linter passed
 		build: bash.#Run & {
-			input: images.goBuilder.output
+			input: baseImages.goBuilder
 
 			env: {
 				GOMODCACHE: mounts["go mod cache"].dest
@@ -71,7 +73,7 @@ engine.#Plan & {
 		}
 
 		goLint: bash.#Run & {
-			input: images.goLinter.output
+			input: baseImages.goLinter
 
 			// FIXME: the source volume is too slow, taking >3m on docker for mac (vs < 2sec on the host machine)
 			script: contents: "golangci-lint run -v --timeout 5m"