deviceshell: Fix racecondition and long running tests

When writing to stdout and stderr from two processes, their output could become
interleaved. To work around that, we write stdout and stderr to different files
and later combine them together in the shell script.

Since tst_deviceshell tests could run for a long time if /usr folder
is too big, added a check that first tests the runtime once.

Since we currently only support linux containers, limit the tests to
only run if the container platform is linux as well.

Change-Id: I4b313596cdf9acc839d54d7cc77c66fd53ac23bf
Reviewed-by: hjk <hjk@qt.io>

src/libs/utils/deviceshell.cpp

@@ -62,8 +62,11 @@ finalOutput() {
     local fileInputBuffer
     while read fileInputBuffer
     do
+        if test -f "$fileInputBuffer.err"; then
+            cat $fileInputBuffer.err
+        fi
         cat $fileInputBuffer
-        rm $fileInputBuffer
+        rm -f $fileInputBuffer.err $fileInputBuffer
     done
 }
 
@@ -117,7 +120,7 @@ executeAndMark()
 
     # Mark the app's output streams
     readAndMark $PID 'O' < "$stdoutenc" >> $TMPFILE &
-    readAndMark $PID 'E' < "$stderrenc" >> $TMPFILE &
+    readAndMark $PID 'E' < "$stderrenc" >> $TMPFILE.err &
 
     # Start the app ...
     if [ -z "$INDATA" ]