infra/pkg-kconfig: do not update-(def)config to a directory

Currently, if the user specifies the path to an existing directory as
the path to the custom (def)config file (FOO_KCONFIG_FILE), then we
happily create a file in there, either 'defconfig' or '.config' (or
whatever the .config is named for that package), depending on whether
we're saving a defconfig or a full config.

So, we could save the file, but then the Buildroot defconfig file that
contains that path would no longer be reusable as-is, because we
interpret that path as a path to a file.

Furthermore, if the directory-portion of FOO_KCONFIG_FILE does not
exist yet, the update would fail, because cp does not create missing
directory components.

So we fix that by adding an explicit test for the directory-ness of the
target file, and then an explicit mkdir to create missing directory
components.

Signed-off-by: "Yann E. MORIN" <yann.morin.1998@free.fr>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>

package/pkg-kconfig.mk

@@ -18,6 +18,11 @@ define kconfig-package-update-config
 		echo "Unable to perform $(@) when fragment files are set"; exit 1)
 	@$(if $($(PKG)_KCONFIG_DEFCONFIG), \
 		echo "Unable to perform $(@) when using a defconfig rule"; exit 1)
+	$(Q)if [ -d $($(PKG)_KCONFIG_FILE) ]; then \
+		echo "Unable to perform $(@) when $($(PKG)_KCONFIG_FILE) is a directory"; \
+		exit 1; \
+	fi
+	$(Q)mkdir -p $(dir $($(PKG)_KCONFIG_FILE))
 	cp -f $($(PKG)_DIR)/$(1) $($(PKG)_KCONFIG_FILE)
 	$(Q)touch --reference $($(PKG)_DIR)/$($(PKG)_KCONFIG_DOTCONFIG) $($(PKG)_KCONFIG_FILE)
 endef