Use a different cache dir in each test file

packages/bun-internal-test/src/runner.node.mjs

@@ -240,6 +240,7 @@ Starting "${name}"
           BUN_RUNTIME_TRANSPILER_CACHE_PATH: "0",
           GITHUB_ACTIONS: process.env.GITHUB_ACTIONS ?? "true",
           BUN_DEBUG_QUIET_LOGS: "1",
+          BUN_INSTALL_CACHE_DIR: join(TMPDIR, ".bun-install-cache"),
           [windows ? "TEMP" : "TMPDIR"]: TMPDIR,
         },
       });