Specify Python3_EXECUTABLE explicitly.

Otherwise `MLIR_BINDINGS_PYTHON_ENABLED=ON` won't work.

build_tools/cmake_configure.sh

@@ -105,6 +105,7 @@ cmake -GNinja \
   "-DNPCOMP_USE_SPLIT_DWARF=ON" \
   "-DCMAKE_CXX_FLAGS_DEBUG=$DEBUG_FLAGS" \
   "-DPYTHON_EXECUTABLE=$python_exe" \
+  "-DPython3_EXECUTABLE=$python_exe" \
   "-DMLIR_DIR=$install_mlir/lib/cmake/mlir" \
   "-DLLVM_EXTERNAL_LIT=$LLVM_LIT" \
   "-DLLVM_ENABLE_WARNINGS=ON" \

build_tools/install_mlir.sh

@@ -67,6 +67,7 @@ cmake -GNinja \
   "-B$build_mlir" \
   -DCMAKE_EXPORT_COMPILE_COMMANDS=TRUE \
   "-DPYTHON_EXECUTABLE=$python_exe" \
+  "-DPython3_EXECUTABLE=$python_exe" \
   -DLLVM_BUILD_LLVM_DYLIB=ON \
   -DLLVM_LINK_LLVM_DYLIB=ON \
   -DLLVM_INSTALL_UTILS=ON \