[build-script] Create time log dir

If the directory where the build time log is supposed to go doesn't
exist, create it. The append file mode will create files, but won't
create directories. When we start building ninja, we haven't necessary
created the build directory yet, so this results in an error about the
missing directory when writing the build time log.

Author: etcwilde

utils/swift_build_support/swift_build_support/utils.py

@@ -48,8 +48,11 @@ def clear_log_time():
 
 
 def log_time(event, command, duration=0):
-    f = open(log_time_path(), "a")
+    log_time_dir = os.path.dirname(log_time_path())
+    if not os.path.isdir(log_time_dir):
+        os.mkdir(log_time_dir)
 
+    f = open(log_time_path(), "a")
     log_event = {
         "event": event,
         "command": command,