finance/kmymoney: fix build on powerpc

ld: error: undefined symbol: __multi3

referenced by mymoneyforecast.cpp

kmymoney/mymoney/CMakeFiles/kmm_mymoney.dir/mymoneyforecast.cpp.o:(MyMoneyForecastPrivate::calculateAccountTrendList())

did you mean: __muldi3
defined in: /usr/lib/libgcc_s.so