buildman: Use spaces in the board list

At present the board names shown with -l are separated by commas. This
makes it hard to double-click to select a particular board. Also it is not
possible to select all boards and paste them as arguments to a subsequent
buildman run, since buildman requires spaces to separate the list on the
command line, not commas.

Change the output format to use spaces instead of commas.

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

tools/buildman/builder.py

@@ -1253,7 +1253,7 @@ class Builder:
                 for line in err_lines:
                     boards = ''
                     names = [board.target for board in line.boards]
-                    board_str = ','.join(names) if names else ''
+                    board_str = ' '.join(names) if names else ''
                     if board_str:
                         out = self.col.Color(colour, line.char + '(')
                         out += self.col.Color(self.col.MAGENTA, board_str,