Full path for -b

[kokizzu]

It would be nice if gin support full path for -b, for example: gin -b /tmp/out.bin

all we need is to modify inside func MainAction(c *cli.Context) {

        //runner := gin.NewRunner(filepath.Join(wd, builder.Binary()), c.Args()...)
        runpath := builder.Binary()
        if runpath[0] != '/' {
                runpath = filepath.Join(wd, runpath)
        }
        runner := gin.NewRunner(runpath, c.Args()...)