switch to revisionistic ATen

The ATen repository appears to have been completely rewritten!
Switch to the commit with the same commit message in the new history.
The CMakeLists.txt file now appears in the aten subdirectory.

Author: Sven Verdoolaege

build.sh

@@ -240,7 +240,7 @@ function install_aten() {
       if should_reconfigure .. .build_cache; then
         echo "Reconfiguring ATen"
         export PYTORCH_PYTHON=${PYTHON}
-        ${CMAKE_VERSION} .. -DCMAKE_INSTALL_PREFIX=${INSTALL_PREFIX} -DHAS_C11_ATOMICS=OFF -DNO_CUDA=${ATEN_NO_CUDA}
+        ${CMAKE_VERSION} ../aten -DCMAKE_INSTALL_PREFIX=${INSTALL_PREFIX} -DHAS_C11_ATOMICS=OFF -DNO_CUDA=${ATEN_NO_CUDA}
       fi
       make -j $CORES -s || exit 1