buildman: Write output even on fatal error

At present buildman does not write any output (to the 'out' and 'err)
files if the build terminates with a fatal error. This is to avoid adding
lots of spam to the logs.

However there are times when this is actually useful, such as when the
build fails for an obscure reason such as a Kconfig loop.

Update the logic to always write the output, so that the user gets a clue
as to what is happening.

Signed-off-by: Simon Glass <sjg@chromium.org>

tools/buildman/builderthread.py

@@ -300,16 +300,12 @@ class BuilderThread(threading.Thread):
             work_in_output: Use the output directory as the work directory and
                 don't write to a separate output directory.
         """
-        # Fatal error
-        if result.return_code < 0:
-            return
-
         # If we think this might have been aborted with Ctrl-C, record the
         # failure but not that we are 'done' with this board. A retry may fix
         # it.
-        maybe_aborted =  result.stderr and 'No child processes' in result.stderr
+        maybe_aborted = result.stderr and 'No child processes' in result.stderr
 
-        if result.already_done:
+        if result.return_code >= 0 and result.already_done:
             return
 
         # Write the output and stderr
@@ -332,6 +328,10 @@ class BuilderThread(threading.Thread):
         elif os.path.exists(errfile):
             os.remove(errfile)
 
+        # Fatal error
+        if result.return_code < 0:
+            return
+
         if result.toolchain:
             # Write the build result and toolchain information.
             done_file = self.builder.GetDoneFile(result.commit_upto,