buildman: Handle commit subjects containing unicode

One of these has crept in in this commit:

40a808f1 ARCv2: SLC: Make sure busy bit is set properly on SLC flushing

Adjust buildman to handle it.

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

tools/buildman/builder.py

@@ -95,8 +95,9 @@ u-boot/             source directory
 # Possible build outcomes
 OUTCOME_OK, OUTCOME_WARNING, OUTCOME_ERROR, OUTCOME_UNKNOWN = range(4)
 
-# Translate a commit subject into a valid filename
-trans_valid_chars = string.maketrans("/: ", "---")
+# Translate a commit subject into a valid filename (and handle unicode)
+trans_valid_chars = string.maketrans('/: ', '---')
+trans_valid_chars = trans_valid_chars.decode('latin-1')
 
 BASE_CONFIG_FILENAMES = [
     'u-boot.cfg', 'u-boot-spl.cfg', 'u-boot-tpl.cfg'