Fix custom plugins when building on a folder different than the source directory
Fix custom plugins when building on a folder different than the source directory

adamsdadakaeti/bzflag,adamsdadakaeti/bzflag,khonkhortisan/bzflag,adamsdadakaeti/bzflag,adamsdadakaeti/bzflag,adamsdadakaeti/bzflag,khonkhortisan/bzflag,khonkhortisan/bzflag,khonkhortisan/bzflag,adamsdadakaeti/bzflag,khonkhortisan/bzflag,khonkhortisan/bzflag,adamsdadakaeti/bzflag,khonkhortisan/bzflag