[source] package/libs/zlib: Add host build

[LEDE Commits]

hauke pushed a commit to source.git, branch master:
https://git.lede-project.org/cbe71649bc49ccc6ae96385482d0794c33336f68

commit cbe71649bc49ccc6ae96385482d0794c33336f68
Author: Daniel Engberg <daniel.engberg.lists at pyret.net>
AuthorDate: Tue Dec 12 15:31:59 2017 +0100

    package/libs/zlib: Add host build
    
    Some packages such as Python/Python3 (host pip/pip3) needs this
    to compile.
    
    More detailed explanation provided by Alexandru:
    
    "i need the zlib/host for Python/Python3 ; because, it seems the
    host pip/pip3 needs this to work ; i suspect in older versions
    this worked, because some of the host's build env would be used
    in the build, and then the zlib-dev from the host distro would
    be used ; now, the host-build does not seem to have any
    -I/usr/include stuff, which is good
    
    and it also seems that Python/Python3 does not like it if the
    zlib-dev package is too old, so using this zlib/host would be
    good for this as well"
    
    Source:
    https://github.com/lede-project/source/pull/1329#issuecomment-351055861
    
    Signed-off-by: Alexandru Ardelean <ardeleanalex at gmail.com>
    Signed-off-by: Daniel Engberg <daniel.engberg.lists at pyret.net>
---
 package/libs/zlib/Makefile | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/package/libs/zlib/Makefile b/package/libs/zlib/Makefile
index 2650faa..94977b0 100644
--- a/package/libs/zlib/Makefile
+++ b/package/libs/zlib/Makefile
@@ -21,6 +21,7 @@ PKG_CPE_ID:=cpe:/a:gnu:zlib
 
 PKG_CONFIG_DEPENDS:= CONFIG_ZLIB_OPTIMIZE_SPEED
 
+include $(INCLUDE_DIR)/host-build.mk
 include $(INCLUDE_DIR)/package.mk
 include $(INCLUDE_DIR)/cmake.mk
 
@@ -96,5 +97,6 @@ define Package/zlib-dev/install
 	  $(1)/usr/lib/pkgconfig/
 endef
 
+$(eval $(call HostBuild))
 $(eval $(call BuildPackage,zlib))
 $(eval $(call BuildPackage,zlib-dev))