Fixes the parcel2 build for hdf5 viz when using node18. The underlying

problem is that parcel passes through, unfiltered, the environment.  We
could have a separate list to figure out which plugins need additional
options, but this runs the risk of deployers having *other* potentially
broken things in their ENV for node.  By telling parcel to just use the
process backend, we avoid this issue completely and don't have to modify
or maintain other changes to the build infra.

client/gulpfile.js

@@ -157,7 +157,11 @@ function buildPlugins(callback, forceRebuild) {
                     };
                     // if node version is >16, set NODE_OPTIONS to use legacy openssl provider
                     if (process.versions.node.split(".")[0] > "16") {
-                        opts.env = { ...process.env, NODE_OPTIONS: "--openssl-legacy-provider" };
+                        opts.env = {
+                            ...process.env,
+                            PARCEL_WORKER_BACKEND: "process",
+                            NODE_OPTIONS: "--openssl-legacy-provider",
+                        };
                     }
                     if (child_process.spawnSync("yarn", ["build"], opts).status === 0) {
                         console.log(`Successfully built, saving build state to ${hashFilePath}`);