sdk: fix missing include directories

It's not possible to compile some applications which are using
`-Werror=missing-include-dirs` compiler flags with the SDK as some
target directories are missing in the SDK tarball:

 cc1: error: staging_dir/target/usr/include: No such file or directory [-Werror=missing-include-dirs]
 cc1: error: staging_dir/target/include: No such file or directory [-Werror=missing-include-dirs]

Fix this by adding the missing directories in the SDK.

Signed-off-by: Petr Štetiar <[email protected]>

target/sdk/Makefile

@@ -82,7 +82,12 @@ KERNEL_FILES := $(patsubst $(TOPDIR)/%,%,$(wildcard $(addprefix $(LINUX_DIR)/,$(
 all: compile
 
 $(BIN_DIR)/$(SDK_NAME).tar.xz: clean
-	mkdir -p $(SDK_BUILD_DIR)/dl $(SDK_BUILD_DIR)/package
+	mkdir -p \
+		$(SDK_BUILD_DIR)/dl \
+		$(SDK_BUILD_DIR)/package \
+		$(SDK_BUILD_DIR)/$(STAGING_SUBDIR_TARGET)/include \
+		$(SDK_BUILD_DIR)/$(STAGING_SUBDIR_TARGET)/usr/include
+
 	$(CP) -L $(INCLUDE_DIR) $(SCRIPT_DIR) $(SDK_BUILD_DIR)/
 	$(TAR) -cf - -C $(TOPDIR) \
 		`cd $(TOPDIR); find $(KDIR_BASE)/ -name \*.ko` \