Solution: generate list of sources and headers with:

 ls -1 src/*cpp | sort | sed 's|src/\(.*\)|      <File RelativePath="..\\..\\..\\..\\src\\\1" />|g'
 ls -1 src/*hpp | sort | sed 's|src/\(.*\)|      <File RelativePath="..\\..\\..\\..\\src\\\1" />|g'

and add them.