package/leveldb: turn snappy into an optional dependency

snappy is not a mandatory dependency to build leveldb. Back when it
was introduced in Buildroot, as of version 1.18, the build logic
already made snappy an optional dependency.

Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>
Signed-off-by: Yann E. MORIN <yann.morin.1998@free.fr>
(cherry picked from commit 39ef24f8bbe44d7850179f10fe0ab7e08e06059d)
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>

package/leveldb/Config.in

@@ -3,7 +3,6 @@ config BR2_PACKAGE_LEVELDB
 	depends on BR2_INSTALL_LIBSTDCPP
 	depends on BR2_TOOLCHAIN_GCC_AT_LEAST_4_8 # C++11
 	depends on BR2_TOOLCHAIN_HAS_THREADS
-	select BR2_PACKAGE_SNAPPY
 	help
 	  LevelDB is a fast key-value storage library written at Google
 	  that provides an ordered mapping from string keys to string

package/leveldb/leveldb.mk

@@ -9,9 +9,12 @@ LEVELDB_SITE = $(call github,google,leveldb,$(LEVELDB_VERSION))
 LEVELDB_LICENSE = BSD-3-Clause
 LEVELDB_LICENSE_FILES = LICENSE
 LEVELDB_INSTALL_STAGING = YES
-LEVELDB_DEPENDENCIES = snappy
 LEVELDB_CONF_OPTS = \
 	-DLEVELDB_BUILD_BENCHMARKS=OFF \
 	-DLEVELDB_BUILD_TESTS=OFF
 
+ifeq ($(BR2_PACKAGE_SNAPPY),y)
+LEVELDB_DEPENDENCIES += snappy
+endif
+
 $(eval $(cmake-package))