update asdf-vm setup to use $ASDF_DIR to work if user defined cus…

…tom directory (#36043)

Summary:
Update setup of sourcing `asdf-vm` in `find-node-for-xcode.sh` in case of user has custom defined of `$ASDF_DIR`
by default `$ASDF_DIR` point to `$HOME/.asdf`, but if user has custom directory (like XDG convention) this script wont work without this change.

## Changelog

<!-- Help reviewers and the release process by writing your own changelog entry.

Pick one each for the category and type tags:

[ANDROID|GENERAL|IOS|INTERNAL] [BREAKING|ADDED|CHANGED|DEPRECATED|REMOVED|FIXED|SECURITY] - Message

For more details, see:
https://reactnative.dev/contributing/changelogs-in-pull-requests
-->
[GENERAL] [CHANGED] - Find node binary when using asdf as the node version manager with custom `$ASDF_DIR`

Pull Request resolved: #36043

Test Plan: use a defualt/custom `$ASDF_DIR` while using `asdf-vm` as node version manager then make iOS build.

Reviewed By: cortinico

Differential Revision: D42990407

Pulled By: cipolleschi

fbshipit-source-id: 1fe3fdc786bddf741ff422e7bec55a6c9cc8ed83

scripts/find-node-for-xcode.sh

@@ -58,7 +58,10 @@ if [[ ! -x node && -d ${HOME}/.anyenv/bin ]]; then
 fi
 
 # Set up asdf-vm if present
-if [[ -f "$HOME/.asdf/asdf.sh" ]]; then
+if [[ -f "$ASDF_DIR/asdf.sh" ]]; then
+  # shellcheck source=/dev/null
+  . "$ASDF_DIR/asdf.sh"
+elif [[ -f "$HOME/.asdf/asdf.sh" ]]; then
   # shellcheck source=/dev/null
   . "$HOME/.asdf/asdf.sh"
 elif [[ -x "$(command -v brew)" && -f "$(brew --prefix asdf)/asdf.sh" ]]; then