One solution is to use sudo instead of su to change to root to run the install. sudo takes the user's password instead of the root password. It can also be configured to allow specific users. It also has command line options to read the password from stdin and display no prompt. 
echo $password | sudo -S -p '' "make install"

[download]
The password can be stored in the script. Or entered once in the top of script.

In reply to Re: Using expect to do make install when installing perl mods by iburrell
in thread Using expect to do make install when installing perl mods by Plankton

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