stdlib: Add GCS support

The interface and behavior is identical to S3.

Signed-off-by: Scott Lewis-Kelly <slewiskelly@slewiskel.ly>

stdlib/gcp/gcs/tests/verify.cue

@@ -0,0 +1,83 @@
+package gcs
+
+import (
+	"alpha.dagger.io/alpine"
+	"alpha.dagger.io/dagger/op"
+	"alpha.dagger.io/gcp"
+)
+
+#List: {
+	// GCP Config
+	config: gcp.#Config
+
+	// Target GCP URL (e.g. gs://<bucket-name>/<path>/<sub-path>)
+	target?: string
+
+	contents: {
+		string
+
+		#up: [
+			op.#Load & {
+				from: #GCloud & {
+					"config": config
+				}
+			},
+
+			op.#Exec & {
+				args: [
+					"/bin/bash",
+					"--noprofile",
+					"--norc",
+					"-eo",
+					"pipefail",
+					"-c",
+					#"""
+					gsutil ls -r \#(target) > /contents
+					"""#,
+				]
+			},
+
+			op.#Export & {
+				source: "/contents"
+				format: "string"
+			},
+		]
+	}
+}
+
+#VerifyGCS: {
+	file:   string
+	config: gcp.#Config
+	target: string
+
+	lists: #List & {
+		"config": config
+		"target": target
+	}
+
+	test: #up: [
+		op.#Load & {
+			from: alpine.#Image & {
+				package: bash: "~5.1"
+			}
+		},
+
+		op.#WriteFile & {
+			dest:    "/test"
+			content: lists.contents
+		},
+
+		op.#Exec & {
+			always: true
+			args: [
+				"/bin/bash",
+				"--noprofile",
+				"--norc",
+				"-eo",
+				"pipefail",
+				"-c",
+				"grep -q \(file) /test",
+			]
+		},
+	]
+}