The tarball from github has same file layout as git repo while the tarball from ftp doesn't.
Update Makefile to accommodate this change.
Signed-off-by: Xu Xingliang <xuxingliang@xiaomi.com>
This option, which resolves to -w when CONFIG_CYGWIN_WINTOOL is
configured, is now appended to INCDIR in tools/Config.mk.
See git commit # 5eae32577e5d5226e5d3027c169eeb369f83f77d in the main