Merge pull request #383 from eliecharra/fix_s3_cache_issue

S3 does not update object if rollbacked to an existing layer

examples/simple-s3/main.cue

@@ -28,6 +28,7 @@ page: """
 deploy: s3.#Put & {
 	config:       awsConfig
 	sourceInline: page
+	always:       true
 	contentType:  "text/html"
 	target:       "s3://\(bucket)/index.html"
 }

stdlib/aws/s3/s3.cue

@@ -26,8 +26,14 @@ import (
 	// URL of the uploaded S3 object
 	url: out
 
+	// Always write the object to S3
+	always?: bool
+
 	out: string
 	aws.#Script & {
+		if always != _|_ {
+			"always": always
+		}
 		files: {
 			if sourceInline != _|_ {
 				"/inputs/source": sourceInline