local UW_SUFFIX="" if [ ! -z "${3}" ]; then UW_SUFFIX="=${3}" fi is the same as UW_SUFFIX="=${3}"
Created attachment 36534 [details] ebuild.sh.diff
Not it isn't. It will leave an equal sign of $3 is empty. --with-blah= is most likely not valid.
oh sorry, just overlooked the equal sign :-/ but wouldn't ${3/*/=${3}} do it then?
Use ${3:+=${3}} instead.