release: Explicitly enable lib32 in make-manifest.sh

[jlduran]

Summary

Explicitly set the lib32 distribution set (32-bit compatibility
libraries) to be selected by default during bsdinstall(8).

While lib32 is currently selected by default, it occurs implicitly
because default_lib32 is unset, falling into a catch-all that defaults
to "on".

The lib32 is selected by default because it is needed by some popular
ports, such as wine and steam.

Test Plan

As described in comment D56528#1294613, at the end of this revision stack, it should match the following:

% sh release/scripts/make-manifest.sh base-dbg.txz base.txz kernel-dbg.txz kernel.txz lib32-dbg.txz lib32.txz ports.txz src.txz tests.txz
base-dbg.txz	0123456789abcdef...	0	base_dbg	"Base system debug info"	off
base.txz	0123456789abcdef...	0	base	"Base system (MANDATORY)"	on
kernel-dbg.txz	0123456789abcdef...	0	kernel_dbg	"Kernel debug info"	off
kernel.txz	0123456789abcdef...	0	kernel	"Kernel (MANDATORY)"	on
lib32-dbg.txz	0123456789abcdef...	0	lib32_dbg	"32-bit compatibility libraries (Debugging)"	off
lib32.txz	0123456789abcdef...	0	lib32	"32-bit compatibility libraries"	on
ports.txz	0123456789abcdef...	0	ports	"Ports tree"	off
src.txz	0123456789abcdef...	0	src	"System source tree"	off
tests.txz	0123456789abcdef...	0	tests	"Test suite"	off

cc/ @senguptaangshuman17_gmail.com

[jrtc27]

What's the justification for changing this long-standing default? I don't see one in the summary. I'm not saying it's the wrong thing to do, but it needs to be clearly stated.

[jlduran]

Yes, I agree. My original plan was to only select the MANDATORY options by default.
But giving it a second thought, maybe I should change it to explicitly set default_lib32 to on (it is currently set to on because there is no default_lib32), and clearly state in the commit that this is to have 32-bit support for some popular ports by default (wine, steam, etc.)?

[jlduran]

Address suggestions:

• Add more context in the commit message
• Leave this setting as is, just change the script to explicilty set it