zlib patch to use std name for lib.

Use a standard name libz.(so|a) if we are using mingw (as we do on linux).

This patch somehow deprecate the previous commit (patch) but both patches
are the right thing to do.
We need this one especially for others dependencies using pkg-config.
The generated .pc always use the '-lz' option and so, we need the correct
names for the lib.

kiwix-build.py

@@ -752,6 +752,7 @@ class zlib(Dependency):
     class Source(ReleaseDownload):
         archive = Remotefile('zlib-1.2.8.tar.gz',
                              '36658cb768a54c1d4dec43c3116c27ed893e88b02ecfcb44f2166f9c0b7f2a0d')
+        patches = ['zlib_std_libname.patch']
 
     class Builder(CMakeBuilder):
         @property

patches/zlib_std_libname.patch

@@ -0,0 +1,15 @@
+diff -ur zlib-1.2.8/CMakeLists.txt zlib-1.2.8.std_libname/CMakeLists.txt
+--- zlib-1.2.8/CMakeLists.txt	2013-04-29 00:57:10.000000000 +0200
++++ zlib-1.2.8.std_libname/CMakeLists.txt	2017-02-07 11:56:21.826507000 +0100
+@@ -205,6 +205,9 @@
+    if(NOT APPLE)
+      set_target_properties(zlib PROPERTIES LINK_FLAGS "-Wl,--version-script,\"${CMAKE_CURRENT_SOURCE_DIR}/zlib.map\"")
+    endif()
++elseif(MINGW)
++    # On unix-like platforms the library is almost always called libz
++   set_target_properties(zlib zlibstatic PROPERTIES OUTPUT_NAME z)
+ elseif(BUILD_SHARED_LIBS AND WIN32)
+     # Creates zlib1.dll when building shared library version
+     set_target_properties(zlib PROPERTIES SUFFIX "1.dll")
+Only in zlib-1.2.8: zconf.h
+Only in zlib-1.2.8.std_libname: zconf.h.included