Adjust tests/standalone/io/file_test not to resolve relative to Platform.executable.

tests/standalone/standalone.status

 # Copyright (c) 2013, the Dart project authors.  Please see the AUTHORS file
 # for details. All rights reserved. Use of this source code is governed by a
 # BSD-style license that can be found in the LICENSE file.
 
 # WARNING:
 # Tests using the multitest feature where failure is expected should *also* be
 # listed in tests/lib/analyzer/analyze_tests.status without the "standalone"
 # prefix.
 
 packages_file_test: Skip # Issue 26715
@@ skipping 186 matching lines @@
 package/scenarios/invalid/invalid_utf8_test: Crash, OK # Analyzer exits on invalid package config
 package/scenarios/invalid/invalid_package_name_test: Crash, OK # Analyzer exits on invalid package config
 package/scenarios/invalid/same_package_twice_test: Crash, OK # Analyzer exits on invalid package config
 
 [ $system == windows ]
 io/skipping_dart2js_compilations_test: Fail # Issue 19551.
 verbose_gc_to_bmu_test: Skip
 io/platform_resolved_executable_test/06: RuntimeError  # Issue 23641
 io/process_sync_test: Pass, Timeout # Issue 24596
 io/sleep_test: Pass, Fail # Issue 25757
-io/file_test: RuntimeError # Issue 27748
 
 [ ($runtime == vm || $runtime == dart_precompiled || $runtime == dart_app) && $mode == debug && $builder_tag == asan ]
 full_coverage_test: Skip  # Timeout.
 io/file_lock_test: Skip  # Timeout.
 io/test_runner_test: Skip  # Timeout.
 io/http_client_stays_alive_test: Skip  # Timeout.
 
 [ ($runtime == vm || $runtime == dart_precompiled || $runtime == dart_app) ]
 # Failures in secure networking while NSS is replaced with BoringSSL
 io/https_client_certificate_test: RuntimeError # Issue 24070
@@ skipping 146 matching lines @@
 package/*: SkipByDesign # Launches VMs in interesting ways.
 
 [ $builder_tag == no_ipv6 ]
 io/http_bind_test: Skip
 io/raw_datagram_socket_test: Skip
 io/socket_source_address_test: Skip
 io/socket_bind_test: Skip
 io/http_proxy_advanced_test: Skip
 io/http_ipv6_test: Skip
 io/socket_ipv6_test: Skip