fix: add some Linux variables to default passthrough env vars (#10959)

### Description

Adds `XDG_RUNTIME_DIR` to the list of default global pass-through
environment variables. This ensures that the standard XDG runtime
directory is available in tasks by default.

### Testing Instructions

Verify that `XDG_RUNTIME_DIR` is passed through to tasks by running a
Turborepo task that prints its environment variables (e.g., `echo
$XDG_RUNTIME_DIR`).

CLOSES TURBO-4894

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Co-authored-by: Cursor Agent <[email protected]>

Author: anthonyshew

crates/turborepo-lib/src/task_hash.rs

@@ -444,6 +444,9 @@ impl<'a> TaskHasher<'a> {
                     "LANG",
                     "SHELL",
                     "PWD",
+                    "XDG_RUNTIME_DIR",
+                    "XAUTHORITY",
+                    "DBUS_SESSION_BUS_ADDRESS",
                     "CI",
                     "NODE_OPTIONS",
                     "COREPACK_HOME",