Simplify & fix node interception approach

Previously we injected into $PATH directly so that we could take
complete control. With NODE_OPTIONS this isn't actually necessary, since
the only option we care about can be set just from env vars directly.
This would've been more difficult to set up back when this was written,
since it was only included in node 8, but it's been backported to 6.12
and node 6 and 8 are both EOL now, so I think we can handle that.

This notably also fixes interception issues with anything that respawns
node using process.execPath (i.e. Yarn) which previously skipped the
hooks setup. Using these env vars instead lets us punch right through
that.

Author: pimterry

overrides/js/prepend-node.js

@@ -4,7 +4,7 @@
  * plus tweaks various other HTTP clients that need nudges, so they
  * all correctly pick up the proxy from the environment.
  *
- * Tested against Node 6, 8, 10 and 12.
+ * Tested against Node 6, 8, 10, 12 and 14.
 */
 
 const wrapModule = require('./wrap-require');

overrides/path/node

@@ -9,6 +9,7 @@ const PATH_VAR_SEPARATOR = process.platform === 'win32' ? ';' : ':';
 export const OVERRIDES_DIR = path.join(APP_ROOT, 'overrides');
 const OVERRIDE_RUBYGEMS_PATH = path.join(OVERRIDES_DIR, 'gems');
 const OVERRIDE_PYTHONPATH = path.join(OVERRIDES_DIR, 'pythonpath');
+const OVERRIDE_JS_SCRIPT = path.join(OVERRIDES_DIR, 'js', 'prepend-node.js');
 
 export const OVERRIDE_BIN_PATH = path.join(OVERRIDES_DIR, 'path');
 
@@ -69,8 +70,9 @@ export function getTerminalEnvVars(
                 ? `${OVERRIDE_PYTHONPATH}:${currentEnv.PYTHONPATH}`
             : OVERRIDE_PYTHONPATH,
 
-        // Clear NODE_OPTIONS - it's meant for _us_, not subprocesses.
-        // Otherwise e.g. --max-http-header-size can break old Node/Electron
-        NODE_OPTIONS: ""
+        // We use $NODE_OPTIONS to prepend our script into node. Notably this also
+        // clears it, which is important, as _our_ NODE_OPTIONS aren't meant for
+        // subprocesses. Otherwise e.g. --max-http-header-size breaks old Node/Electron.
+        NODE_OPTIONS: `--require "${OVERRIDE_JS_SCRIPT}"`
     };
 }