src: check for --prof in ParseArgs

[evanlucas]

Previously, all of the cli arguments are parsed and then we loop
through the v8 arguments again. This patch removes the need for the
additional loop as we can check if the argument is --prof during the
initial ParseArgs.

[bnoordhuis]

I guess I don't really see the point. The number of comparisons stays the same, right?

[evanlucas]

The number of comparisons doesn't change, but it prevents the additional loop through v8_argv. I trust your opinion though, so if you think it is worthless, I can close :]

[bnoordhuis]

I suspect it's basically a wash and possibly a pico-deoptimization. The loop counter probably lives in a register but v8_is_profiling is almost certainly reloaded from memory every time it's checked.

[evanlucas]

works for me