First, try using the -VV option along with those options so you can see the full output of configure -there may be some problem you are not seeing.
Try using single quotes instead of duble quotes:
To be honest, I doubt that will work, but it's worth trying. That option syntax is not found very frequently -what version of squid are you trying to build? If you tell me then I can try it out here and maybe fix that so it works if it doesn't work as above.
Also, try having src2pkg write a basic script for you, by using the -N option along with whatever else you are using. You may find that the options work when used from a script.
In the worst case, use src2pkg to create a script, then edit it by commenting out the 'configure_source' statement and replace it with:
CFLAGS=-O2 -march=i486 -mtune=i686 ./configure --prefix=/opt/squid --enable-carp --enable-icmp --enable-delay-pools --enable-arp-acl --enable-htcp --enable-forw-via-db --enable-cache-digests --enable-ssl --with-openssl --enable-linux-netfilter --with-large-files --enable-large-cache-files --enable-auth="basic, digest" --enable-basic-auth-helpers="NCSA, getpwnam" --enable-digest-auth-helpers="password" --with-external-acl-helpers="unix, ip" --enable-storeio="ufs, aufs"
Thanks for reporting and let me know how it goes.