tools: always create $STAGING_DIR/usr/{include,lib}

tools: always create $STAGING_DIR/usr/{include,lib}

rules.mk always passes these as -I/-L to the toolchain.

Fixes rare errors like:
cc1: error: staging_dir/target-aarch64_cortex-a53_musl/usr/include: No such file or directory [-Werror=missing-include-dirs]

Signed-off-by: Andre Heider <a.heider@gmail.com>
Acked-by: Paul Spooren <mail@aparcar.org>
Acked-by: Rosen Penev <rosenp@gmail.com>
[fixed merge conflict]
Signed-off-by: Petr Štetiar <ynezz@true.cz>
(cherry picked from commit b0cb305236524095bfd899449b0ad8eb821cb3bb)