rules.mk: define rule for running (f)lex
rules.mk: define rule for running (f)lex

Planned JAQL comes with a first shot lexer generated by flex.

zyzyis/monetdb,zyzyis/monetdb,zyzyis/monetdb,zyzyis/monetdb,zyzyis/monetdb,zyzyis/monetdb,zyzyis/monetdb,zyzyis/monetdb,zyzyis/monetdb,zyzyis/monetdb