Avoid copying folders that are not present in CI

Summary:
This Diff is a copy of this [PR](facebook#34223) that we have against 0.69-stable.

This Diff introduces some checks to prevent that we try to copy folders that are not present.

## Changelog

Avoid copying the folders when they are not there.

[General] [Changed] - When preparing the Hermes workspace, we don't copy the folders that are not present.

Differential Revision: D37961092

fbshipit-source-id: f52f73a53a93dcb549d5c5cbf714e3ba242ada9a

.circleci/config.yml

@@ -899,8 +899,17 @@ jobs:
           name: Download Hermes tarball
           command: |
             node scripts/hermes/prepare-hermes-for-build
-            cp sdks/download/* $HERMES_WS_DIR/download/.
-            cp -r sdks/hermes/* $HERMES_WS_DIR/hermes/.
+
+            # If Hermes is not built from source, we don't have these folders.
+            DOWNLOAD_FOLDER=sdks/download/
+            if [[ -d $DOWNLOAD_FOLDER ]]; then
+              cp $DOWNLOAD_FOLDER* $HERMES_WS_DIR/download/.
+            fi
+
+            HERMES_FOLDER=sdks/hermes/
+            if [[ -d $HERMES_FOLDER ]]; then
+              cp -r $HERMES_FOLDER* $HERMES_WS_DIR/hermes/.
+            fi
       - save_cache:
           key: *hermes_cache_key
           paths: