[openwrt/openwrt] rules.mk: drop `include_mk` build rule

[LEDE Commits]

neoraider pushed a commit to openwrt/openwrt.git, branch master:
https://git.lede-project.org/cfdfa6d04e16b001e45054dafbf5df3cfc98ef03

commit cfdfa6d04e16b001e45054dafbf5df3cfc98ef03
Author: Alexandru Ardelean <ardeleanalex at gmail.com>
AuthorDate: Wed Jan 24 12:56:39 2018 +0200

    rules.mk: drop `include_mk` build rule
    
    The only users of this were the python packages
    from the `packages` feed.
    The 2 python interpreters would export some mk
    files (e.g. python-package.mk) and then other
    python packages would include it via this rule.
    
    But there's a few things wrong with this approach,
    most of them drawing from the fact that python host
    needs to be built first, to export these mk files.
    
    By now all uses of include_mk have been corrected
    in the feeds and this can be removed.
    
    Signed-off-by: Alexandru Ardelean <ardeleanalex at gmail.com>
---
 rules.mk | 4 ----
 1 file changed, 4 deletions(-)

diff --git a/rules.mk b/rules.mk
index 9d8b9f8..84e0aaa 100644
--- a/rules.mk
+++ b/rules.mk
@@ -355,10 +355,6 @@ define shexport
 export $(call shvar,$(1))=$$(call $(1))
 endef
 
-define include_mk
-$(eval -include $(if $(DUMP),,$(STAGING_DIR)/mk/$(strip $(1))))
-endef
-
 # Execute commands under flock
 # $(1) => The shell expression.
 # $(2) => The lock name. If not given, the global lock will be used.