Due to CMP0080, BundleUtilities can no longer be included at
configure-time. However, DeployQt4 contains some functions which
are meant to be used at configure-time, and some which are meant
to be used at install-time and use BundleUtilities. This change
breaks the file into two sections: common functions and install-time
functions. BundleUtilities is now only included at install-time,
thus fixing the policy warning.

Fixes: #18466