demo: use --set-section-alignment when using objcopy

If we don't set the alignment then there is a chance that it ends up
commonly on a 4-byte boundary and GResources will have to malloc/memcpy
the static data.

With --set-section-alignment (which takes a byte offset not ^2) available
in objcopy >= 2.33 we ensure that expectation is met.

demos/gtk-demo/meson.build

@@ -206,6 +206,7 @@ if can_use_objcopy_for_resources
     output : 'gtkdemo_resources2.o',
     command : [objcopy,
                  '--strip-all',
+                 '--set-section-alignment', '.data=8',
                  '--add-symbol','_g_binary_gtkdemo_resource_data=.data:0',
                  '@INPUT@',
                  '@OUTPUT@'])