Also set $0 for binary files

Also set `$0` for bytecode ruby files

Before this patch:

	$ echo 'puts "$0=#{$0}"' > demo.rb && ./build/host/bin/mruby demo.rb 
	$0=demo.rb

	$ ./build/host/bin/mrbc demo.rb && ./build/host/bin/mruby -b demo.mrb 
	$0=

	$ ./build/host/bin/mruby -e 'puts "$0=#{$0}"'
	$0=-e

After this patch:

	$ echo 'puts "$0=#{$0}"' > demo.rb && ./build/host/bin/mruby demo.rb
	$0=demo.rb
	
	$ ./build/host/bin/mrbc demo.rb && ./build/host/bin/mruby -b demo.mrb 
	$0=demo.mrb
	
	$ ./build/host/bin/mruby -e 'puts "$0=#{$0}"'
	$0=-e