build: fix icu-i18n pkg-config version check

The pkg_config() helper can either return a tuple of None values
(no pkg-config installed) and that was what the check was testing
for, but it can also return a tuple of empty strings when the
package isn't installed.

PR-URL: https://github.com/nodejs/node/pull/28118


Reviewed-By: Richard Lau <riclau@uk.ibm.com>
Reviewed-By: Rich Trott <rtrott@gmail.com>
Reviewed-By: Refael Ackermann (רפאל פלחי) <refack@gmail.com>
Reviewed-By: Michael Dawson <michael_dawson@ca.ibm.com>
Reviewed-By: James M Snell <jasnell@gmail.com>