buildman: fix typo

Fix a typo in the error message from CheckOutputDir().

Signed-off-by: Chris Packham <judge.packham@gmail.com>
Reviewed-by: Simon Glass <sjg@chromium.org>
diff --git a/tools/buildman/control.py b/tools/buildman/control.py
index 27916d3..fcf531c 100644
--- a/tools/buildman/control.py
+++ b/tools/buildman/control.py
@@ -99,7 +99,7 @@
     cwd_path = os.path.realpath('.')
     while True:
         if os.path.realpath(path) == cwd_path:
-            Print("Cannot use output directory '%s' since it is within the current directtory '%s'" %
+            Print("Cannot use output directory '%s' since it is within the current directory '%s'" %
                   (path, cwd_path))
             sys.exit(1)
         parent = os.path.dirname(path)