gd: restore png, zlib, and tiff in the default PACKAGECONFIG

Before the PACKAGECONFIG conversion, png, zlib, and tiff support was
always enabled: those libraries were in DEPENDS and autoconf picked
them up automatically because no --without-* flag was passed for them.
The conversion introduced a regression by not including them in the
default PACKAGECONFIG, causing the mechanism to emit --without-png,
--without-zlib, and --without-tiff, silently disabling those features.

Evidence from the configure logs:

  pre-conversion:
    --with-jpeg=<sysroot>/usr/lib/.. --with-freetype=yes
    --without-fontconfig --without-webp --without-xpm --without-x
    (no --with/--without for png, zlib, or tiff; autoconf detects them)

  post-conversion, unfixed:
    --with-freetype --with-jpeg
    --without-png --without-tiff --without-zlib   <-- regression

  post-conversion, fixed:
    --with-freetype --with-jpeg
    --with-png --with-tiff --with-zlib             <-- restored

Add png, zlib, and tiff to the default PACKAGECONFIG so the out-of-
the-box feature set is unchanged from before the conversion.

Fixes: be9f029b6c ("gd: Support PACKAGECONFIG")
AI-Generated: codex/claude-sonnet 4.6 (high)
Signed-off-by: Trevor Woerner <twoerner@gmail.com>
Signed-off-by: Khem Raj <khem.raj@oss.qualcomm.com>

meta-oe/recipes-support/gd/gd_2.3.3.bb

@@ -23,7 +23,7 @@ SRCREV = "b5319a41286107b53daa0e08e402aa1819764bdc"
 
 inherit autotools binconfig gettext pkgconfig
 
-PACKAGECONFIG ?= "jpeg freetype"
+PACKAGECONFIG ?= "jpeg png zlib tiff freetype"
 
 PACKAGECONFIG[avif] = "--with-avif,--without-avif"
 PACKAGECONFIG[fontconfig] = "--with-fontconfig,--without-fontconfig"