cmake: Add missing source file

Author: piponazo

src/CMakeLists.txt

@@ -137,7 +137,7 @@ generate_export_header(exiv2lib
 
 if( EXIV2_ENABLE_PNG )
     set(PUBLIC_HEADERS ${PUBLIC_HEADERS} ../include/exiv2/pngimage.hpp)
-    target_sources(exiv2lib_int PRIVATE pngchunk_int.cpp)
+    target_sources(exiv2lib_int PRIVATE pngchunk_int.cpp pngchunk_int.hpp)
     target_sources(exiv2lib PRIVATE pngimage.cpp ../include/exiv2/pngimage.hpp)
 endif()