[nautilus] configure: check for introspection macro before calling it

[Cosimo Cecchi <cosimoc src gnome org>]

commit cea06af55baf8a2644c1b1afd6fe6d09c813dbc2
Author: Andrés G. Aragoneses <knocte gmail com>
Date:   Tue Jun 18 15:45:14 2013 +0200

    configure: check for introspection macro before calling it
    
    In case the person building nautilus didn't have introspection,
    autoconf was not failing when finding the call to
    GOBJECT_INTROSPECTION_CHECK. After, automake would
    throw this kind of cryptic message (which hints about
    introspection not being present, but also smells like a
    bug in the autotools scripts waiting to be fixed):
    
    ...
    eel/Makefile.am: installing './depcomp'
    parallel-tests: installing './test-driver'
    libnautilus-extension/Makefile.am:67: error: HAVE_INTROSPECTION does not appear in AM_CONDITIONAL
    
    We can improve this by checking if the macro is defined before
    calling it, which would then not pose any problem in case the
    user wants to build without introspection support.
    
    https://bugzilla.gnome.org/show_bug.cgi?id=702554

 configure.ac |    4 +++-
 1 files changed, 3 insertions(+), 1 deletions(-)
---
diff --git a/configure.ac b/configure.ac
index 85c2cb8..b9fa84d 100644
--- a/configure.ac
+++ b/configure.ac
@@ -295,7 +295,9 @@ AC_CHECK_HEADERS([X11/XF86keysym.h])
 ##################################################
 # Check for introspection
 ##################################################
-GOBJECT_INTROSPECTION_CHECK([0.6.4])
+m4_ifdef([GOBJECT_INTROSPECTION_CHECK],
+       [GOBJECT_INTROSPECTION_CHECK([0.6.4])],
+       [AM_CONDITIONAL(HAVE_INTROSPECTION, false)])
 
 dnl ==========================================================================