The fixpack5 setup.exe is a common Installshield type exe that calls a fix.msi. The command line for the exe can be constucted as follows to pass the required MSI parameters properly
setup.exe /s /v"/qb-! /l*v %temp%\fixpack5.log"
note the quotes enclosing the parameters after the /v.
Alternatively calling msi directly can also work with the following
msiexec /i fix.msi /qb-! SETUPEXEDIR=<folder containing setup.exe> /l*v %temp%\fixpack5.log
