gtk3: disable use of to-pixdata during build

to-pixdata is not available during build. errors shown below.
if pixdata is made available, then subsequent errors with shared-mime
occur. this disable rebuild of pngs.

[3/665] Generating gtkresources_c with a custom command
FAILED: gtk/gtkresources.c
/storage/home-rudi/LibreELEC.tv/build.LibreELEC-Generic.x86_64-10.0-devel/toolchain/bin/glib-compile-resources gtk/gtk.gresources.xml --sourcedir /storage/home-rudi/LibreELEC.tv/build.LibreELEC-Generic.x86_64-10.0-devel/build/gtk3-3.24.28/.x86_64-libreelec-linux-gnu/gtk --sourcedir /storage/home-rudi/LibreELEC.tv/build.LibreELEC-Generic.x86_64-10.0-devel/build/gtk3-3.24.28/gtk --sourcedir ../gtk --c-name _gtk --internal --generate --target gtk/gtkresources.c --manual-register --dependency-file
gtk/gtkresources.c.d
gtk/gtk.gresources.xml: to-pixdata preprocessing requested, but GDK_PIXBUF_PIXDATA is not set, and gdk-pixbuf-pixdata is not in PATH.
[4/665] Generating gtkresources_h with a custom command
FAILED: gtk/gtkresources.h
/storage/home-rudi/LibreELEC.tv/build.LibreELEC-Generic.x86_64-10.0-devel/toolchain/bin/glib-compile-resources gtk/gtk.gresources.xml --sourcedir /storage/home-rudi/LibreELEC.tv/build.LibreELEC-Generic.x86_64-10.0-devel/build/gtk3-3.24.28/.x86_64-libreelec-linux-gnu/gtk --sourcedir /storage/home-rudi/LibreELEC.tv/build.LibreELEC-Generic.x86_64-10.0-devel/build/gtk3-3.24.28/gtk --sourcedir ../gtk --c-name _gtk --internal --generate --target gtk/gtkresources.h --manual-register
gtk/gtk.gresources.xml: to-pixdata preprocessing requested, but GDK_PIXBUF_PIXDATA is not set, and gdk-pixbuf-pixdata is not in PATH.

packages/addons/addon-depends/chrome-depends/gtk3/patches/disable-to-pixdata-build.patch

@@ -0,0 +1,26 @@
+--- a/gtk/gen-gtk-gresources-xml.py	2021-02-24 19:13:19.000000000 +0000
++++ b/gtk/gen-gtk-gresources-xml.py	2021-04-03 23:52:35.000000000 +0000
+@@ -23,11 +23,6 @@
+     <file>theme/Adwaita/gtk-contained-dark.css</file>
+ '''
+
+-for f in get_files('theme/Adwaita/assets', '.png'):
+-  xml += '    <file preprocess=\'to-pixdata\'>theme/Adwaita/assets/{0}</file>\n'.format(f)
+-
+-xml += '\n'
+-
+ for f in get_files('theme/Adwaita/assets', '.svg'):
+   xml += '    <file>theme/Adwaita/assets/{0}</file>\n'.format(f)
+
+@@ -38,11 +33,6 @@
+     <file>theme/HighContrast/gtk-contained-inverse.css</file>
+ '''
+
+-for f in get_files('theme/HighContrast/assets', '.png'):
+-  xml += '    <file preprocess=\'to-pixdata\'>theme/HighContrast/assets/{0}</file>\n'.format(f)
+-
+-xml += '\n'
+-
+ for f in get_files('theme/HighContrast/assets', '.svg'):
+   xml += '    <file>theme/HighContrast/assets/{0}</file>\n'.format(f)
+