[gnome-panel] pkgconfig: avoid warning about datarootdir

[Alberts Muktupāvels <muktupavels src gnome org>]

commit 16c147b699f49a02c1c047ddd369f637d5553d2d
Author: Alberts Muktupāvels <alberts muktupavels gmail com>
Date:   Sat Mar 7 22:01:09 2020 +0200

    pkgconfig: avoid warning about datarootdir
    
    config.status: WARNING:  'data/pkgconfig/libgnome-panel.pc.in'
    seems to ignore the --datarootdir setting

 data/pkgconfig/libgnome-panel.pc.in | 1 +
 1 file changed, 1 insertion(+)
---
diff --git a/data/pkgconfig/libgnome-panel.pc.in b/data/pkgconfig/libgnome-panel.pc.in
index 569c72a03..c0e90b90d 100644
--- a/data/pkgconfig/libgnome-panel.pc.in
+++ b/data/pkgconfig/libgnome-panel.pc.in
@@ -2,6 +2,7 @@ prefix=@prefix@
 exec_prefix=@exec_prefix@
 libdir=@libdir@
 includedir=@includedir@
+datarootdir=@datarootdir@
 layoutsdir=@datadir@/gnome-panel/layouts
 modulesdir=@libdir@/gnome-panel/modules