[seahorse/ricotz/vala] Unbreak build using vala 0.48.x

[Rico Tzschichholz <ricotz src gnome org>]

commit d6611fec6664c12f7f0e6e1d87b153867ccc6cca
Author: Rico Tzschichholz <ricotz ubuntu com>
Date:   Sun Feb 28 19:03:10 2021 +0100

    Unbreak build using vala 0.48.x
    
    bc26f2bf5cb3035f0f94c412f3e675d2071b1ed4 causes a redefinition error due
    to including "seahorse-common.h".
    
    Using --use-header for "common" lib avoids this problem.

 common/meson.build | 1 +
 1 file changed, 1 insertion(+)
---
diff --git a/common/meson.build b/common/meson.build
index 52e57c8a..b1d10efc 100644
--- a/common/meson.build
+++ b/common/meson.build
@@ -38,6 +38,7 @@ common_deps = [
 
 common_vala_args = [
   '--gresources', resources_xml,
+  '--use-header',
 ]
 
 if get_option('keyservers-support')