How to enable SOCKS5 for Squid proxy?

Have a look at this page. It talks about squid socks support and how you can build it to support SOCKS connections. The status is "testing". So, you may need to think about using it for production.

When building squid, you need to define these variables:

export CFLAGS=" -Dbind=SOCKSbind "
export CXXFLAGS=" -Dbind=SOCKSbind "
export LDADD=" -lsocks "

to modify build and link options.

Also, you can pass these variables to configure script. If you have already built squid, you can find out the current values using squid -v. This will show you squid version along with configure and build options.