build: Add a CMake config file compatible with the FindPNG module

Co-authored-by: Cosmin Truta <ctruta@gmail.com>
Signed-off-by: Cosmin Truta <ctruta@gmail.com>

CMakeLists.txt

@@ -1129,6 +1129,30 @@ if(NOT SKIP_INSTALL_EXPORT AND NOT SKIP_INSTALL_ALL)
           FILE libpng${PNGLIB_ABI_VERSION}.cmake)
 endif()
 
+# Create a CMake Config File that can be used via find_package(PNG CONFIG)
+if(NOT SKIP_INSTALL_CONFIG_FILE AND NOT SKIP_INSTALL_ALL)
+  install(TARGETS ${PNG_LIBRARY_TARGETS}
+          EXPORT PNGTargets
+          RUNTIME DESTINATION ${CMAKE_INSTALL_BINDIR}
+          LIBRARY DESTINATION ${CMAKE_INSTALL_LIBDIR}
+          ARCHIVE DESTINATION ${CMAKE_INSTALL_LIBDIR}
+          FRAMEWORK DESTINATION ${CMAKE_INSTALL_LIBDIR})
+
+  include(CMakePackageConfigHelpers)
+  write_basic_package_version_file(PNGConfigVersion.cmake
+                                   VERSION ${PNGLIB_VERSION}
+                                   COMPATIBILITY SameMinorVersion)
+
+  install(EXPORT PNGTargets
+          FILE PNGTargets.cmake
+          NAMESPACE PNG::
+          DESTINATION ${CMAKE_INSTALL_LIBDIR}/cmake/PNG)
+
+  install(FILES ${CMAKE_CURRENT_SOURCE_DIR}/scripts/cmake/PNGConfig.cmake
+                ${CMAKE_CURRENT_BINARY_DIR}/PNGConfigVersion.cmake
+          DESTINATION ${CMAKE_INSTALL_LIBDIR}/cmake/PNG)
+endif()
+
 # TODO: Create MSVC import lib for MinGW-compiled shared lib.
 # pexports libpng.dll > libpng.def
 # lib /def:libpng.def /machine:x86