rbutil: Fix native Windows build for tools.

- When make on Windows finds sh.exe it will try to use that. We use
  cmd.exe calls when detecting Windows, so make sure we use cmd.exe as
  shell.
- Add missing Windows compatibility to tomcrypt Makefile.

Change-Id: Iaef133ca27472a5ddf449174d540983f15c66aea

tools/ucl/src/Makefile

@@ -13,6 +13,7 @@ SILENT = @
 endif
 
 ifeq ($(OS),Windows_NT)
+SHELL = cmd.exe
 mkdir = if not exist $(subst /,\,$(1)) mkdir $(subst /,\,$(1))
 else
 mkdir = mkdir -p $(1)