Add missed CMake include for check_include_file

Issue #2820

diff --git a/cmake/OpenCVFindLibsGrfmt.cmake b/cmake/OpenCVFindLibsGrfmt.cmake
index 08af604..33e428b 100644 (file)
--- a/cmake/OpenCVFindLibsGrfmt.cmake
+++ b/cmake/OpenCVFindLibsGrfmt.cmake
@@ -116,6 +116,7 @@ if(WITH_PNG AND NOT IOS)
   else()
     include(FindPNG)
     if(PNG_FOUND)
+      include(CheckIncludeFile)
       check_include_file("${PNG_PNG_INCLUDE_DIR}/png.h"        HAVE_PNG_H)
       check_include_file("${PNG_PNG_INCLUDE_DIR}/libpng/png.h" HAVE_LIBPNG_PNG_H)
       if(HAVE_PNG_H)