squid4: add "-lresolv" to kerberos variant

[TP75]

Refering to ​

• https://trac.macports.org/ticket/57652#comment:4

Description

Type(s)

• bugfix
• enhancement
• security fix

Tested on

macOS 10.13.6 17G3025
Xcode 10.1 10B61

Verification

Have you

• followed our Commit Message Guidelines?
• squashed and minimized your commits?
• checked that there aren't other open pull requests for the same change?
• referenced existing tickets on Trac with full URL?

• checked your Portfile with port lint?
• tried existing tests with sudo port test?
• tried a full install with sudo port -vst install?
• tested basic functionality of all binary files?

[macportsbot]

Notifying maintainers:
@jmroot for port squid4.

[macportsbot]

Travis Build #4381 Passed.

Lint results

--->  Verifying Portfile for squid4
--->  0 errors and 0 warnings found.

Port squid4 success on xcode9.4. Log
Port squid4 success on xcode8.3. Log
Port squid4 success on xcode7.3. Log
Port squid4 success on xcode10.1. Log

[jmroot]

No revision increase should be done when fixing a build failure.

[TP75]

Interesting. How to diffenrentiate between the Portfile versions?

Loooking into the MacPorts Guide 5.4. Global Keywords there are:

1. version - The version of the ported software. (not the version of the port)
2. revision - used to track port revisions.
3. epoch - must be used when a port is updated to a version that is numerically less than the previous version

What did I miss?