tools/makemanifest.py: Use os.makedirs to make path for generated files.

The existing implementation of mkdir() in this file is not sophisticated
enough to work correctly on all operating systems (eg Mac can raise
EISDIR).  Using the standard os.makedirs() function handles all cases
correctly.

Signed-off-by: Damien George <damien@micropython.org>

tools/makemanifest.py

@@ -25,7 +25,6 @@
 # THE SOFTWARE.
 
 from __future__ import print_function
-import errno
 import sys
 import os
 import subprocess
@@ -165,17 +164,10 @@ def get_timestamp_newest(path):
     return ts_newest
 
 
-def mkdir(path):
-    cur_path = ""
-    for p in path.split("/")[:-1]:
-        cur_path += p + "/"
-        try:
-            os.mkdir(cur_path)
-        except OSError as er:
-            if er.args[0] == errno.EEXIST:
-                pass
-            else:
-                raise er
+def mkdir(filename):
+    path = os.path.dirname(filename)
+    if not os.path.isdir(path):
+        os.makedirs(path)
 
 
 def freeze_internal(kind, path, script, opt):