Move PETBUILD_GTK to _00build.conf

[dimkr]

This will be useful if:

1. @mrfricks decides to use GTK+ 2 to make his next Puppy closer to FossaPup 9.5 (https://forum.puppylinux.com/viewtopic.php?f=40&t=4138)
2. @peabee wants to use GTK+ 2 in a 64-bit build not based on an old distro like Ubuntu 18.04; the automatic PETBUILD_GTK choice logic in petbuilds.sh (what we have today) will pick GTK+ 3
3. @01micko decides to stick with GTK+ 2 for Slacko 8.x, and deal with GTK+ 3 related issues later, possibly in a point release
4. I want to build a "lite" or "barebones" 64-bit flavor of dpup that uses the lighter GTK+ 2

[01micko]

Looks good from my perspective.

[mrfricks]

there's only a few gtkdialog apps that i kept as gtk2 as i found gtk3 problematic with them.
they are quicksetup (i found selecting the timezone a chore), samba simple management (doesn't display properly) and the PPM (i use an older version that works well but gtk3 removes various install & info bars)

everything else is gtk3

[dimkr]

there's only a few gtkdialog apps that i kept as gtk2 as i found gtk3 problematic with them. they are quicksetup (i found selecting the timezone a chore), samba simple management (doesn't display properly) and the PPM (i use an older version that works well but gtk3 removes various install & info bars)

Can you open a PR that makes these problematic apps use gtk2dialog?

[01micko]

@mrfricks I forced pMusic to use gtk2, perhaps you could do something similar for the gtkdialog apps you need to run with gtk2. (see rootfs-packages/pmusic).

[mrfricks]

i can do a PR for samba in petbuilds but for quicksetup i actually just used fossapups version as just running it with gtk2dialog doesn't solve the selection list issue.

as for the PPM i use an older version so a PR wouldn't be appropriate ... unless it is a complete roll back to the last good working version :) #2186

@01micko yes i have done that with a few apps. most are working well with gtk3 though and look nicer.

[01micko]

Well let's merge then 😃