[gobject-introspection] Makefile.introspection: Allow usage with --header-only

[Colin Walters <walters src gnome org>]

commit 60d0ec439957b76aff2ed0add44e5a7f9bba69dc
Author: Colin Walters <walters verbum org>
Date:   Wed Oct 19 15:46:29 2011 -0400

    Makefile.introspection: Allow usage with --header-only

 Makefile.introspection |    3 ++-
 1 files changed, 2 insertions(+), 1 deletions(-)
---
diff --git a/Makefile.introspection b/Makefile.introspection
index a0764ac..228cdde 100644
--- a/Makefile.introspection
+++ b/Makefile.introspection
@@ -120,7 +120,8 @@ define introspection-scanner
 
 # Basic sanity check, to make sure required variables are set
 $(if $($(_gir_name)_FILES),,$(error Need to define $(_gir_name)_FILES))
-$(if $(or $($(_gir_name)_LIBS),
+$(if $(or $(findstring --header-only,$($(_gir_name)_SCANNERFLAGS)),
+          $($(_gir_name)_LIBS),
           $($(_gir_name)_PROGRAM)),,
     $(error Need to define $(_gir_name)_LIBS or $(_gir_name)_PROGRAM))