zstd: fix host headers installation

zstd: fix host headers installation

If host-zstd builds when $(HOST_DIR)/include has not been created yet,
the install-includes target does not create this directory. Instead, the
install command copies the headers over $(HOST_DIR)/include, thus
creating a regular file instead of a directory. This leads to the
following installation failure:

Installing includes
install: cannot create directory ‘.../host/usr/include/’: File exists
Makefile:166: recipe for target 'install-pc' failed
make[1]: *** [install-pc] Error 1

Add a patch to fix that.

Cc: Peter Seiderer <ps.report@gmx.net>
Cc: Andrey Smirnov <andrew.smirnov@gmail.com>
Signed-off-by: Baruch Siach <baruch@tkos.co.il>
Reviewed-by: Peter Seiderer <ps.report@gmx.net>
Reviewed-by: "Yann E. MORIN" <yann.morin.1998@free.fr>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>