standalone/FileTest crashes when running multiple tests

[ghost]

Running tests with --mode=all crashes standalone/FileTest because two binaries (release and debug) are accessing the same file ("tests/vm/data/fixed_length_file_out_truncate"). The crash has been confirmed on Mac OS X. The solution is probably to to use a unique name.

=== debugia32 vm standalone/FileTest ===
Path: standalone/FileTest
Unhandled exception:
Expect.fail('testTruncate: No errors expected')
 0. Function: 'Expect._fail@127eafe4' url: 'bootstrap' line:1078 col:5
 1. Function: 'Expect.fail' url: 'bootstrap' line:893 col:10
 2. Function: 'FileTest.function' url: '/sources/dall/dart/tests/standalone/src/FileTest.dart' line:335 col:18
 3. Function: '[email protected]' url: 'dart:builtin' line:1271 col:22
 4. Function: '[email protected]' url: 'dart:builtin' line:1122 col:15
 5. Function: 'ReceivePortSingleShotImpl.function' url: 'bootstrap_impl' line:1728 col:15
 6. Function: 'ReceivePortImpl._handleMessage@924b4b8' url: 'bootstrap_impl' line:1707 col:22
Command: xcodebuild/Debug_ia32/dart --ignore-unrecognized-flags /sources/dall/dart/tests/standalone/src/FileTest.dart

[DartBot]

This comment was originally written by [email protected]

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Added Area-Test, Triaged labels.

[whesse]

Fixing this by placing the modified files in a temporary directory, which is guaranteed to be not shared.

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cc @madsager.
cc @sgjesse.
Set owner to @whesse.
Added Accepted label.

[whesse]

Fixed in r2020.

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Added Fixed label.