package: add support for <pkg>_BUSYBOX_CONFIG_FIXUPS

This will allow individual packages to define extra Busybox options
that they need.

Signed-off-by: Francois Perrad <francois.perrad@gadz.org>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>

docs/manual/adding-packages-generic.adoc

@@ -631,6 +631,12 @@ different steps of the build process.
   This is seldom used, as package usually have no strict requirements on
   the kernel options.
 
+* +LIBFOO_BUSYBOX_CONFIG_FIXUPS+ lists the Busybox configuration
+  options that are needed to use this package especially in some scripts,
+  or at contrario the useless options. This shall be a set of
+  calls to one of the kconfig tweaking option: `KCONFIG_ENABLE_OPT`,
+  `KCONFIG_DISABLE_OPT`, or `KCONFIG_SET_OPT`.
+
 The preferred way to define these variables is:
 
 ----

package/busybox/busybox.mk

@@ -422,6 +422,7 @@ define BUSYBOX_KCONFIG_FIXUP_CMDS
 	$(BUSYBOX_SET_SELINUX)
 	$(BUSYBOX_SET_LESS_FLAGS)
 	$(BUSYBOX_SET_INDIVIDUAL_BINARIES)
+	$(PACKAGES_BUSYBOX_CONFIG_FIXUPS)
 endef
 
 define BUSYBOX_BUILD_CMDS

package/pkg-generic.mk

@@ -1242,6 +1242,9 @@ endif
 ifneq ($$($(2)_USERS),)
 PACKAGES_USERS += $$($(2)_USERS)$$(sep)
 endif
+ifneq ($$($(2)_BUSYBOX_CONFIG_FIXUPS),)
+PACKAGES_BUSYBOX_CONFIG_FIXUPS += $$($(2)_BUSYBOX_CONFIG_FIXUPS)$$(sep)
+endif
 ifneq ($$($(2)_LINUX_CONFIG_FIXUPS),)
 PACKAGES_LINUX_CONFIG_FIXUPS += $$($(2)_LINUX_CONFIG_FIXUPS)$$(sep)
 endif