Issue #12618: py_compile cannot create files in current directory

Initial patch by Sjoerd de Vries.
diff --git a/Lib/py_compile.py b/Lib/py_compile.py
index e0f98cb..5adb70a 100644
--- a/Lib/py_compile.py
+++ b/Lib/py_compile.py
@@ -130,7 +130,9 @@
         else:
             cfile = imp.cache_from_source(file)
     try:
-        os.makedirs(os.path.dirname(cfile))
+        dirname = os.path.dirname(cfile)
+        if dirname:
+            os.makedirs(dirname)
     except OSError as error:
         if error.errno != errno.EEXIST:
             raise