Remove bin/erl before replacing it
Remove bin/erl before replacing it

In some erlang distributions (e.g. brew) the ERTS files do not have 
write permissions set.  When this is the case the file:write_file will
fail with error 'eacces'.

This commit removes 'bin/erl' before attempting to write the new file.
bsmr-erlang/relx,umatomba/relx,timclassic/relx,zugolosian/relx,RJ/relx,priestjim/relx,Licenser/relx,erlware/relx,tsloughter/relx,syl20bnr/relx,bitwalker/relx,ingwinlu/relx,lrascao/relx,ethercrow/relx