File libmng-2.0.3-install-pc-file.patch of Package mingw64-libmng

--- libmng-2.0.3/CMakeLists.txt.orig	2023-07-05 19:50:42.163878363 +0200
+++ libmng-2.0.3/CMakeLists.txt	2023-07-05 19:51:08.020043384 +0200
@@ -434,7 +434,7 @@
 #
 ENDIF(BUILD_SHARED_LIBS)
 #------------ libmng.pc ---------------
-IF(UNIX)
+IF(UNIX OR MINGW)
  SET(MNG_LIBS_PRIVATE "")
  IF(JPEG_FOUND)
   SET(MNG_LIBS_PRIVATE "${MNG_LIBS_PRIVATE} -ljpeg")