cmake: include the current directory's ConfigureChecks.cmake
cmake: include the current directory's ConfigureChecks.cmake

The file we want is always in the same directory. The
`ConfigureChecks.cmake` file is included in many projects and the wrong
`CMAKE_MODULE_PATH` can cause the wrong one to be used here.

libexpat/libexpat,libexpat/libexpat,libexpat/libexpat,libexpat/libexpat,libexpat/libexpat,libexpat/libexpat