[LyX/master] zlib: enable prefix, fix mingw build

[Peter Kümmel]

commit dde4f93894adb018c76d12077942f3c5da827b18
Author: Peter Kümmel <kuem...@lyx.org>
Date:   Tue Jan 12 20:11:31 2016 +0100

    zlib: enable prefix, fix mingw build

diff --git a/3rdparty/zlib/CMakeLists.txt b/3rdparty/zlib/CMakeLists.txt
index de6de6a..c29081f 100644
--- a/3rdparty/zlib/CMakeLists.txt
+++ b/3rdparty/zlib/CMakeLists.txt
@@ -75,6 +75,7 @@ endif()
 
 #set(ZLIB_PC ${CMAKE_CURRENT_BINARY_DIR}/zlib.pc)
 #configure_file( ${CMAKE_CURRENT_SOURCE_DIR}/zlib.pc.cmakein ${ZLIB_PC} @ONLY)
+set(Z_PREFIX 1)
 configure_file(${SRCDIR}/zconf.h.cmakein ${CMAKE_BINARY_DIR}/zconf.h @ONLY)
 include_directories(${CMAKE_CURRENT_BINARY_DIR} ${CMAKE_SOURCE_DIR} 
${CMAKE_BINARY_DIR})