vcpkg/ports/libpng/pkgconfig.2.patch

diff --git a/CMakeLists.txt b/CMakeLists.txt
index 6451fcf..4090f42 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -821,20 +821,31 @@ endif()
 # Only do this on Windows for Cygwin - the files don't make much sense outside
 # of a UNIX look-alike.
 if(NOT WIN32 OR CYGWIN OR MINGW)
-  set(prefix      ${CMAKE_INSTALL_PREFIX})
-  set(exec_prefix ${CMAKE_INSTALL_PREFIX})
-  set(libdir      ${CMAKE_INSTALL_FULL_LIBDIR})
-  set(includedir  ${CMAKE_INSTALL_FULL_INCLUDEDIR})
-  set(LIBS        "-lz -lm")
-  configure_file(${CMAKE_CURRENT_SOURCE_DIR}/libpng.pc.in
-    ${CMAKE_CURRENT_BINARY_DIR}/${PNGLIB_NAME}.pc @ONLY)
-  create_symlink(libpng.pc FILE ${PNGLIB_NAME}.pc)
-
-  configure_file(${CMAKE_CURRENT_SOURCE_DIR}/libpng-config.in
-    ${CMAKE_CURRENT_BINARY_DIR}/${PNGLIB_NAME}-config @ONLY)
-  create_symlink(libpng-config FILE ${PNGLIB_NAME}-config)
+  set(LIBS        "-lz")
+  if(NOT APPLE)
+    string(APPEND LIBS " -lm")
+  endif()
+else()
+  if(CMAKE_BUILD_TYPE STREQUAL "DEBUG")
+    set(LIBS "-lzlibd")
+  else()
+    set(LIBS "-lzlib")
+  endif()
 endif()
 
+set(prefix      ${CMAKE_INSTALL_PREFIX})
+set(exec_prefix ${CMAKE_INSTALL_PREFIX})
+set(libdir      ${CMAKE_INSTALL_FULL_LIBDIR})
+set(includedir  ${CMAKE_INSTALL_FULL_INCLUDEDIR})
+
+configure_file(${CMAKE_CURRENT_SOURCE_DIR}/libpng.pc.in
+  ${CMAKE_CURRENT_BINARY_DIR}/${PNGLIB_NAME}.pc @ONLY)
+create_symlink(libpng.pc FILE ${PNGLIB_NAME}.pc)
+
+configure_file(${CMAKE_CURRENT_SOURCE_DIR}/libpng-config.in
+  ${CMAKE_CURRENT_BINARY_DIR}/${PNGLIB_NAME}-config @ONLY)
+create_symlink(libpng-config FILE ${PNGLIB_NAME}-config)
+
 # SET UP LINKS
 if(PNG_SHARED)
   set_target_properties(png PROPERTIES