Remove directory from dockerfiles target (#37258)

* Remove directory from dockerfiles target

Produce a docker build context tarball without a top-level directory to
match the expected format for downstream automation.

This will produce:

```
$ tar -tzf target/kibana-8.0.0-docker-build-context.tar.gz
Dockerfile
bin/
config/
bin/kibana-docker
config/kibana.yml
```

Instead of:

```
$ tar -tzf target/kibana-8.0.0-docker-build-context.tar.gz
kibana-8.0.0-docker-build-context/Dockerfile
kibana-8.0.0-docker-build-context/bin/
kibana-8.0.0-docker-build-context/config/
kibana-8.0.0-docker-build-context/bin/kibana-docker
kibana-8.0.0-docker-build-context/config/kibana.yml
```

* Use options object for root directory config

src/dev/build/lib/fs.js

@@ -188,8 +188,8 @@ export async function untar(source, destination, extractOptions = {}) {
 
 export async function compress(type, options = {}, source, destination) {
   const output = fs.createWriteStream(destination);
-  const archive = archiver(type, options);
-  const name = source.split(sep).slice(-1)[0];
+  const archive = archiver(type, options.archiverOptions);
+  const name = (options.createRootDirectory ? source.split(sep).slice(-1)[0] : false);
 
   archive.pipe(output);
 

src/dev/build/tasks/create_archives_task.js

@@ -34,11 +34,36 @@ export const CreateArchivesTask = {
 
       switch (path.extname(destination)) {
         case '.zip':
-          await compress('zip', { zlib: { level: 9 } }, source, destination);
+          await compress(
+            'zip',
+            {
+              archiverOptions: {
+                zlib: {
+                  level: 9
+                }
+              },
+              createRootDirectory: true
+            },
+            source,
+            destination
+          );
           break;
 
         case '.gz':
-          await compress('tar', { gzip: true, gzipOptions: { level: 9 } }, source, destination);
+          await compress(
+            'tar',
+            {
+              archiverOptions: {
+                gzip: true,
+                gzipOptions: {
+                  level: 9
+                }
+              },
+              createRootDirectory: true
+            },
+            source,
+            destination
+          );
           break;
 
         default:

src/dev/build/tasks/os_packages/docker_generator/bundle_dockerfiles.js

@@ -59,10 +59,13 @@ export async function bundleDockerFiles(config, log, build, scope) {
   await compress(
     'tar',
     {
-      gzip: true,
-      gzipOptions: {
-        level: 9
-      }
+      archiverOptions: {
+        gzip: true,
+        gzipOptions: {
+          level: 9
+        }
+      },
+      createRootDirectory: false
     },
     dockerFilesBuildDir,
     dockerFilesOutputDir