Cause whatcomp output to use the incoming epocroot value. i.e. if epocroot is relative then so is the what output.
e.g. if EPOCROOT=\ then the output will be of the form "\epoc32\release\armv5\...." If it's "..\myepocroot" then the output will be "..\myepocroot\epoc32\release\armv5". If it's absolute then the what output will also be absolute.