[BUG] OpenSearch Dashboards build script references env node version

[kavilla]

Describe the bug

Here we reference NODE="/usr/local/bin/node" but first we check the node executable first [ -x "${DIR}/node/bin/node" ]. If the executable exists we should be using it ie line 20 should say NODE=${DIR}/node/bin/node.

Issue on Darwin when running node 16 globally.

Expected behavior
If building for node 10.24.1, we should use the node executable if its available.

OpenSearch Version
Unreleased 1.2

Dashboards Version
Unreleased 1.2

Plugins

n/a

Screenshots

n/a

Host/Environment (please complete the following information):
Darwin

Additional context

Change came in for allowing FreeBSD, will seek guidance to make sure we do not just undo what we did for FreeBSD.

[smortex]

That looks like an error that slept through the multiple iterations of reworking the FreeBSD support Pull Request.

 if [ -x "${DIR}/node/bin/node" ]; then
-  NODE="/usr/local/bin/node"
+  NODE="${DIR}/node/bin/node"
 else
   NODE="$(which node)"
 fi

should be fine!