graphics/gtk-update-icon-cache: postpone cairo-xlib.pc check

[jbeich]

Summary

Restore rP297047 accidentally reverted by rP313633. This ensures cairo is installed before the check is triggered. It also eliminates the need to use .include <bsd.port.pre.mk> to use ${LOCALBASE}.

Let's go a step further and invoke pkg-config as the port already has USES=pkgconfig and convert ${ECHO_CMD} to ${ECHO_MSG} per Porter's Handbook.

Test Plan

poudriere testport -P builds: 93i386, 93amd64, 101i386, 102amd64

[rfyu28uyeg_snkmail.com]

Looks good. Thanks, Jan.

[rfyu28uyeg_snkmail.com]

That's ugly (my id which is my anti-spam email address). I wonder if phabricator has a setting to override that -- John Hein

[kwm]

This looks good, could you update gtk20 and gtk30 Makefile too with the same change? Thanks

[jbeich]

In D4260#89837, @kwm wrote:

This looks good, could you update gtk20 and gtk30 Makefile too with the same change? Thanks

Done. gtk30 required one more nit before killing .include line: rP402344.