[tests] Attempt to fix flaky standalone/io/named_pipe_type_test

This test has been failing the following error:

Unhandled exception:
Expect.fail('../itxkmd5wzq/named_pipeTGADTD/typeScript: Error: Error when reading '../itxkmd5wzq/named_pipeTGADTD/typeScript': No such file or directory
')

This could happen if the script file has not been written to disk
by the time a sub-process is started.

In order to fix that, non-awaited File.writeAsString is replaced
with File.writeAsStringSync.

TEST=standalone/io/named_pipe_type_test

Change-Id: Ied68c458a04e7c2a5eb20131bea459cb628e1d97
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/417085
Commit-Queue: Alexander Markov <alexmarkov@google.com>
Reviewed-by: Alexander Aprelev <aam@google.com>

https://dart.googlesource.com/sdk/+/325cd9ececbb3576a8b0a4ee634891f8755a0463

DEPS

diff --git a/DEPS b/DEPS
index 0d13cd5..d10fe3b 100644
--- a/DEPS
+++ b/DEPS
@@ -238,7 +238,7 @@
 ]
 
 deps = {
-  'flutter/engine/src/flutter/third_party/dart': Var('dart_git') + '/sdk' + '@' + '4e00733aece25ecddaa03335f328944d064bd26a',
+  'flutter/engine/src/flutter/third_party/dart': Var('dart_git') + '/sdk' + '@' + '325cd9ececbb3576a8b0a4ee634891f8755a0463',
 
   'flutter': Var('flutter_git') + '/mirrors/flutter' + '@' + 'b6921e1895f6002f5930f70c2152cb7704798bf9',
 

commits.json

diff --git a/commits.json b/commits.json
index dba7569..9f2851e 100644
--- a/commits.json
+++ b/commits.json
@@ -1,4 +1,4 @@
 {
   "flutter":"b6921e1895f6002f5930f70c2152cb7704798bf9",
-  "flutter/engine/src/flutter/third_party/dart":"4e00733aece25ecddaa03335f328944d064bd26a"
+  "flutter/engine/src/flutter/third_party/dart":"325cd9ececbb3576a8b0a4ee634891f8755a0463"
 }
\ No newline at end of file