roken: do not require use of rk_mkdir on all platforms

Although rk_mkdir can be provided on all platforms there is no
reason to require that it be used by unconditionally mapping

  mkdir -> rk_mkdir

Change-Id: Ic149500037abf446434332bf6ba67dfb3906cd72

windows/NTMakefile.config

@@ -90,6 +90,9 @@ NO_LOCALNAME=1
 # No entropy-gathering daemon on Windows
 NO_RAND_EGD_METHOD=1
 
+# Windows CRT mkdir does not have the mode parameter
+MKDIR_DOES_NOT_HAVE_MODE=1
+
 # Disable build of installers
 !ifndef NO_INSTALLERS
 BUILD_INSTALLERS=1