Fix broken zlib dependency, update it from 1.2.11 to 1.2.12 (#9764)

Summary:
Zlib (https://www.zlib.net/) has been updated to 1.2.12 due to CVE-2018-25032

- https://nvd.nist.gov/vuln/detail/CVE-2018-25032
- https://github.com/madler/zlib/issues/605

The source .tar.gz is no longer available, and the Makefile for rocksdb now fails as a result. This PR updates the dependency to the newer (and available) version, 1.2.12

Pull Request resolved: https://github.com/facebook/rocksdb/pull/9764

Reviewed By: ajkr

Differential Revision: D35220367

Pulled By: jay-zhuang

fbshipit-source-id: 1f68ff8f048a6dba42077f048ac143468f0e2478

Makefile

@@ -2044,8 +2044,8 @@ ROCKSDB_JAVADOCS_JAR = rocksdbjni-$(ROCKSDB_JAVA_VERSION)-javadoc.jar
 ROCKSDB_SOURCES_JAR = rocksdbjni-$(ROCKSDB_JAVA_VERSION)-sources.jar
 SHA256_CMD = sha256sum
 
-ZLIB_VER ?= 1.2.11
+ZLIB_VER ?= 1.2.12
-ZLIB_SHA256 ?= c3e5e9fdd5004dcb542feda5ee4f0ff0744628baf8ed2dd5d66f8ca1197cb1a1
+ZLIB_SHA256 ?= 91844808532e5ce316b3c010929493c0244f3d37593afd6de04f71821d5136d9
 ZLIB_DOWNLOAD_BASE ?= http://zlib.net
 BZIP2_VER ?= 1.0.8
 BZIP2_SHA256 ?= ab5a03176ee106d3f0fa90e381da478ddae405918153cca248e682cd0c4a2269