packages_base_manual_install.sh: fix for 32-bit machines.

Previously this incorrectly assumes that the machine is 64-bit. Now it incorrectly assumes that it is either 32-bit or 64-bit. It still assumes it is Ubuntu or similar.
Merge pull request #1047 from learning-unlimited/fix_installpackages_32bit

packages_base_manual_install.sh: fix for 32-bit machines.