tools: zlib: switch to git source

Switch to the git repository source so that we can use zstd
compression algorithm to create smaller package tarball. This
patch also corrected the license file name[1].

[1] madler/zlib@352cb28

Suggested-by: Christian Marangi <ansuelsmth@gmail.com>
Signed-off-by: Shiji Yang <yangshiji66@qq.com>
Link: openwrt/openwrt#17880
Signed-off-by: Robert Marko <robimarko@gmail.com>

Author: DragonBluep

tools/zlib/Makefile

@@ -11,12 +11,13 @@ PKG_NAME:=zlib
 PKG_VERSION:=1.3.1
 PKG_RELEASE:=1
 
-PKG_SOURCE:=$(PKG_NAME)-$(PKG_VERSION).tar.gz
-PKG_SOURCE_URL:=https://github.com/madler/zlib/releases/download/v$(PKG_VERSION)
-PKG_HASH:=9a93b2b7dfdac77ceba5a558a580e74667dd6fede4585b91eefb60f03b72df23
+PKG_SOURCE_PROTO:=git
+PKG_SOURCE_URL:=https://github.com/madler/zlib
+PKG_SOURCE_VERSION:=51b7f2abdade71cd9bb0e7a373ef2610ec6f9daf
+PKG_MIRROR_HASH:=6558577038f4839057fad93afb295bf32e84dc9bd2c33512d40a5eab6d4889ef
 
 PKG_LICENSE:=Zlib
-PKG_LICENSE_FILES:=README
+PKG_LICENSE_FILES:=LICENSE
 PKG_CPE_ID:=cpe:/a:zlib:zlib
 
 HOST_BUILD_PARALLEL:=1