Fix podspec_source_build_from_local_source_dir to ensure the artifacts_dir exists before downloading into it (#47698)

Summary:
In its current for the `podspec_source_build_from_local_source_dir` makes an assumption in the existence of the `artifacts_dir` ("Pods/hermes-engine-artifacts"). This is okay in the case where the `pod install` command is first ran without sitting the `REACT_NATIVE_OVERRIDE_HERMES_DIR` because of

1948076b81/packages/react-native/sdks/hermes-engine/hermes-utils.rb (L227)

In a clean checkout however, this results in an error when archiving the Hermes directory due to the missing parent directory of the archive's destination.
This PR suggests adding a check for and optional creation of the existence of the archive directory before usage.

An alternative that I considered was ensuring the existence inside of the `artifacts_dir` function:

1948076b81/packages/react-native/sdks/hermes-engine/hermes-utils.rb (L198-L200)

But there's only one other call site, which already does the `mkdir -p`.

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[IOS] [FIXED] - Ensure artifacts directory exists when building Hermes from local source

Pull Request resolved: https://github.com/facebook/react-native/pull/47698

Test Plan:
I verified the fix by:

- Doing a local git clone of the `hermes` repository.
- Ensure no `Pods` directory exists.
- `export REACT_NATIVE_OVERRIDE_HERMES_DIR=/your/local/path/to/hermes` pointing to the local `hermes` repository.
- Run `pod install`

Reviewed By: cipolleschi

Differential Revision: D66162175

Pulled By: dmytrorykun

fbshipit-source-id: 322633e217063e7ca199b9a9602e279df5fbdb70

packages/react-native/sdks/hermes-engine/hermes-utils.rb

@@ -126,7 +126,9 @@ def podspec_source_build_from_local_source_dir(react_native_path)
     source_dir_path = ENV['REACT_NATIVE_OVERRIDE_HERMES_DIR']
     if Dir.exist?(source_dir_path)
         hermes_log("Using source code from local path: #{source_dir_path}")
-        tarball_path = File.join(artifacts_dir(), "hermes-engine-from-local-source-dir.tar.gz")
+        tarball_dir_path = artifacts_dir()
+        FileUtils.mkdir_p(tarball_dir_path) unless Dir.exist?(tarball_dir_path)
+        tarball_path = File.join(tarball_dir_path, "hermes-engine-from-local-source-dir.tar.gz")
         exclude_paths = [
             "__tests__",
             "./external/flowtest",