Use exec instead of popen to run ign-launch binary (#300)

See gazebosim/gz-launch#151 for more context.

Signed-off-by: Addisu Z. Taddese <[email protected]>

src/cmd/cmdtransport.rb.in

@@ -51,16 +51,6 @@ class Cmd
  end
 
  # Drop command from list of arguments
- Open3.popen2e(exe_name, *args[1..-1]) do |_in, out_err, wait_thr|
- begin
- out_err.each do |line|
- print line
- end
- exit(wait_thr.value.exitstatus)
- rescue Interrupt => e
- print e.message
- exit(-1)
- end
- end
+ exec(exe_name, *args[1..-1])
  end
 end