[libpng16] Conditionalize the install rules for MINGW and CYGWIN

in CMakeLists.txt
diff --git a/ANNOUNCE b/ANNOUNCE
index 6375879..a3885fd 100644
--- a/ANNOUNCE
+++ b/ANNOUNCE
@@ -133,6 +133,7 @@
     the option the tests written in configure itself fail compilation because
     they cause compiler warnings.
   Rewrote autogen.sh to run autoreconf instead of running tools one-by-one.
+  Conditionalize the install rules for MINGW and CYGWIN in CMakeLists.txt
 
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diff --git a/CHANGES b/CHANGES
index 5512b02..c7aee5e 100644
--- a/CHANGES
+++ b/CHANGES
@@ -3884,6 +3884,7 @@
     the option the tests written in configure itself fail compilation because
     they cause compiler warnings.
   Rewrote autogen.sh to run autoreconf instead of running tools one-by-one.
+  Conditionalize the install rules for MINGW and CYGWIN in CMakeLists.txt
 
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diff --git a/CMakeLists.txt b/CMakeLists.txt
index 1f49076..ad0c635 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -245,18 +245,18 @@
 # Only do this on Windows for Cygwin - the files don't make much sense outside
 # a UNIX look alike
 if(NOT WIN32 OR CYGWIN OR MINGW) 
-set(prefix      ${CMAKE_INSTALL_PREFIX})
-set(exec_prefix ${CMAKE_INSTALL_PREFIX})
-set(libdir      ${CMAKE_INSTALL_PREFIX}/${CMAKE_INSTALL_LIBDIR})
-set(includedir  ${CMAKE_INSTALL_PREFIX}/include)
-set(LIBS        "-lz -lm")
-configure_file(${CMAKE_CURRENT_SOURCE_DIR}/libpng.pc.in
-  ${CMAKE_CURRENT_BINARY_DIR}/${PNGLIB_NAME}.pc @ONLY)
-CREATE_SYMLINK(${PNGLIB_NAME}.pc libpng.pc)
+  set(prefix      ${CMAKE_INSTALL_PREFIX})
+  set(exec_prefix ${CMAKE_INSTALL_PREFIX})
+  set(libdir      ${CMAKE_INSTALL_PREFIX}/${CMAKE_INSTALL_LIBDIR})
+  set(includedir  ${CMAKE_INSTALL_PREFIX}/include)
+  set(LIBS        "-lz -lm")
+  configure_file(${CMAKE_CURRENT_SOURCE_DIR}/libpng.pc.in
+    ${CMAKE_CURRENT_BINARY_DIR}/${PNGLIB_NAME}.pc @ONLY)
+  CREATE_SYMLINK(${PNGLIB_NAME}.pc libpng.pc)
 
-configure_file(${CMAKE_CURRENT_SOURCE_DIR}/libpng-config.in
-  ${CMAKE_CURRENT_BINARY_DIR}/${PNGLIB_NAME}-config @ONLY)
-CREATE_SYMLINK(${PNGLIB_NAME}-config libpng-config)
+  configure_file(${CMAKE_CURRENT_SOURCE_DIR}/libpng-config.in
+    ${CMAKE_CURRENT_BINARY_DIR}/${PNGLIB_NAME}-config @ONLY)
+  CREATE_SYMLINK(${PNGLIB_NAME}-config libpng-config)
 endif(NOT WIN32 OR CYGWIN OR MINGW)
 
 # SET UP LINKS
@@ -334,10 +334,13 @@
   install(FILES ${libpng_public_hdrs}   DESTINATION include/${PNGLIB_NAME})
 endif()
 if(NOT SKIP_INSTALL_EXECUTABLES AND NOT SKIP_INSTALL_ALL )
-  install(PROGRAMS ${CMAKE_CURRENT_BINARY_DIR}/libpng-config DESTINATION bin)
-  install(PROGRAMS ${CMAKE_CURRENT_BINARY_DIR}/${PNGLIB_NAME}-config
-          DESTINATION bin)
+  if(NOT WIN32 OR CYGWIN OR MINGW)
+    install(PROGRAMS ${CMAKE_CURRENT_BINARY_DIR}/libpng-config DESTINATION bin)
+    install(PROGRAMS ${CMAKE_CURRENT_BINARY_DIR}/${PNGLIB_NAME}-config
+            DESTINATION bin)
+  endif(NOT WIN32 OR CYGWIN OR MINGW)
 endif()
+
 if(NOT SKIP_INSTALL_FILES AND NOT SKIP_INSTALL_ALL )
   # Install man pages
   if(NOT PNG_MAN_DIR)
@@ -346,14 +349,16 @@
   install(FILES libpng.3 libpngpf.3      DESTINATION ${PNG_MAN_DIR}/man3)
   install(FILES png.5                    DESTINATION ${PNG_MAN_DIR}/man5)
   # Install pkg-config files
-  install(FILES ${CMAKE_CURRENT_BINARY_DIR}/libpng.pc
-          DESTINATION ${CMAKE_INSTALL_LIBDIR}/pkgconfig)
-  install(PROGRAMS ${CMAKE_CURRENT_BINARY_DIR}/libpng-config
-          DESTINATION bin)
-  install(FILES ${CMAKE_CURRENT_BINARY_DIR}/${PNGLIB_NAME}.pc
-          DESTINATION ${CMAKE_INSTALL_LIBDIR}/pkgconfig)
-  install(PROGRAMS ${CMAKE_CURRENT_BINARY_DIR}/${PNGLIB_NAME}-config
-          DESTINATION bin)
+  if(NOT WIN32 OR CYGWIN OR MINGW)
+    install(FILES ${CMAKE_CURRENT_BINARY_DIR}/libpng.pc
+            DESTINATION ${CMAKE_INSTALL_LIBDIR}/pkgconfig)
+    install(PROGRAMS ${CMAKE_CURRENT_BINARY_DIR}/libpng-config
+            DESTINATION bin)
+    install(FILES ${CMAKE_CURRENT_BINARY_DIR}/${PNGLIB_NAME}.pc
+            DESTINATION ${CMAKE_INSTALL_LIBDIR}/pkgconfig)
+    install(PROGRAMS ${CMAKE_CURRENT_BINARY_DIR}/${PNGLIB_NAME}-config
+            DESTINATION bin)
+  endif(NOT WIN32 OR CYGWIN OR MINGW)
 endif()
 
 # On versions of CMake that support it, create an export file CMake