sysutils/tracker3: fix meson configuration on i386

Tracker's meson script has a check for "4-digit year modifier for
strftime", but it semi-intentially uses a date which does not work on
i386, due to its 32-bit time_t. Since we will never fix the Y2038
problem on i386, work around the bad test by using 1970-01-01 instead.

PR: 272017
Reported by: jbeich
MFH: 2023Q2