gnome-themes-standard: drop .la file as unused

oe-core commit 51b3ee298635b11d5784caaa0ac1c8f4034c25a5
[gnome-themes-standard: Fix packages so dev-pkgs image generation
works] disabled generation of the -dev pkg. Since a libtool archive
file was no longer being picked up by the -dev pkg the build will fail
with a QA issue (if ERROR_QA includes installed-vs-shipped):

ERROR: gnome-themes-standard-3.22.3-r0 do_package: QA Issue:
gnome-themes-standard: Files/directories were installed but not
shipped in any package:
/usr/lib64/gtk-2.0/2.10.0/engines/libadwaita.la

The libtool archive file is mostly useless in modern Linux with a
single shared library file so instead of including this in the -dev
pkg we simply drop it.

(From OE-Core rev: 77797a95569252024fca094d33ae9ecbc833597f)

Signed-off-by: Mark Asselstine <mark.asselstine@windriver.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

meta/recipes-gnome/gnome/gnome-themes-standard_3.22.3.bb

@@ -25,6 +25,9 @@ do_install_append() {
         # Only building Adwaita, remove highcontrast files
         rm -rf ${D}${prefix}/share/themes/HighContrast \
                ${D}${prefix}/share/icons
+
+	# The libtool archive file is unneeded with shared libs on modern Linux
+	rm -rf ${D}${libdir}/gtk-2.0/2.10.0/engines/libadwaita.la
 }
 
 # There could be gnome-theme-highcontrast as well but that requires