Building math/octave with QT4?

[Steve Kargl]

Is it possible to build math/octave with QT4?
The recent switch to require QT5 in r469260
leads to an unusable octave (unless one's
intention is to debug QT5).

% gdb81 /usr/local/libexec/octave/4.4.0/exec/amd64-portbld-freebsd12.0/octave-gui octave-gui.core
> bt
#0  0x00000002056b244d in QVariant::QVariant(QVariant const&) ()
   from /usr/local/lib/qt5/libQt5Core.so.5
[Current thread is 1 (LWP 101275)]
(gdb) bt
#0  0x00000002056b244d in QVariant::QVariant(QVariant const&) ()
   from /usr/local/lib/qt5/libQt5Core.so.5
#1  0x0000000227c233c9 in ?? ()
   from /usr/local/lib/qt5/plugins/sqldrivers/libqsqlite.so
#2  0x0000000227c1eba2 in ?? ()
   from /usr/local/lib/qt5/plugins/sqldrivers/libqsqlite.so
#3  0x0000000205117351 in QSqlResult::execBatch(bool) ()
   from /usr/local/lib/qt5/libQt5Sql.so.5
#4  0x0000000203cf9ca2 in ?? () from /usr/local/lib/qt5/libQt5Help.so.5
#5  0x0000000203cfbd42 in ?? () from /usr/local/lib/qt5/libQt5Help.so.5
#6  0x00000002054b24ea in ?? () from /usr/local/lib/qt5/libQt5Core.so.5
#7  0x0000000200d7e426 in thread_start (curthread=0x232679100)
    at /usr/src/lib/libthr/thread/thr_create.c:291
#8  0x0000000000000000 in ?? ()
Backtrace stopped: Cannot access memory at address 0x7fffbebf4000

-- 
Steve