libgit2: do not use a bundled zlib

libgit2 depends on zlib. If libgit2's build system does not find a
system zlib, then it compiles a bundled version of it, which is not
really great. So instead, add zlib as a mandatory dependency.

Signed-off-by: Nicolas Cavallari <nicolas.cavallari@green-communications.fr>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>

package/libgit2/Config.in

@@ -1,5 +1,6 @@
 config BR2_PACKAGE_LIBGIT2
 	bool "libgit2"
+	select BR2_PACKAGE_ZLIB
 	help
 	  libgit2 is a portable, pure C implementation of the Git core
 	  methods provided as a linkable library with a solid API,

package/libgit2/libgit2.mk

@@ -16,6 +16,8 @@ LIBGIT2_CONF_OPTS = \
 	-DUSE_ICONV=ON \
 	-DTHREADSAFE=$(if $(BR2_TOOLCHAIN_HAS_THREADS),ON,OFF)
 
+LIBGIT2_DEPENDENCIES = zlib
+
 # If libiconv is available (for !locale toolchains), then we can use
 # it for iconv support. Note that USE_ICONV=ON is still correct even
 # without libiconv because (1) most toolchain have iconv support
@@ -25,11 +27,6 @@ ifeq ($(BR2_PACKAGE_LIBICONV),y)
 LIBGIT2_DEPENDENCIES += libiconv
 endif
 
-# No option to explicitly enable/disable zlib
-ifeq ($(BR2_PACKAGE_ZLIB),y)
-LIBGIT2_DEPENDENCIES += zlib
-endif
-
 ifeq ($(BR2_PACKAGE_LIBSSH2),y)
 LIBGIT2_DEPENDENCIES += libssh2
 LIBGIT2_CONF_OPTS += -DUSE_SSH=ON