fix: The amalgam

Author: Tania Mathern

scripts/amalgamate.cmake

@@ -49,8 +49,15 @@ set(C2PA_INTERNAL_HPP "${C2PA_SOURCE_DIR}/c2pa_internal.hpp")
 if(NOT EXISTS "${C2PA_INTERNAL_HPP}")
     message(FATAL_ERROR "amalgamate.cmake: c2pa_internal.hpp not found: ${C2PA_INTERNAL_HPP}")
 endif()
-file(READ "${C2PA_INTERNAL_HPP}" INTERNAL_CONTENT)
-file(APPEND "${C2PA_AMALGAM_OUTPUT}" "${INTERNAL_CONTENT}")
+file(STRINGS "${C2PA_INTERNAL_HPP}" INTERNAL_LINES)
+set(INTERNAL_FILTERED "")
+foreach(LINE IN LISTS INTERNAL_LINES)
+    string(FIND "${LINE}" "#include \"" IDX)
+    if(IDX LESS 0)
+        string(APPEND INTERNAL_FILTERED "${LINE}\n")
+    endif()
+endforeach()
+file(APPEND "${C2PA_AMALGAM_OUTPUT}" "${INTERNAL_FILTERED}")
 file(APPEND "${C2PA_AMALGAM_OUTPUT}" "\n")
 
 # Handle includes manually