[gtk+] autogen.sh: fail faster/clearer if g-i not found

[Andrés Aragoneses <aaragoneses src gnome org>]

commit e16f8f218243a01b2c54fd275abc07952dbd010b
Author: Andrés G. Aragoneses <knocte gmail com>
Date:   Sun Mar 2 09:51:47 2014 +0100

    autogen.sh: fail faster/clearer if g-i not found
    
    GOBJECT_INTROSPECTION_CHECK macro can be missing if introspection
    is not installed, so this way the following error is prevented:
    
    "gtk/Makefile.am:1324: error: HAVE_INTROSPECTION does not appear
    in AM_CONDITIONAL"
    
    https://bugzilla.gnome.org/show_bug.cgi?id=723438

 autogen.sh |   12 ++++++++++++
 1 files changed, 12 insertions(+), 0 deletions(-)
---
diff --git a/autogen.sh b/autogen.sh
index 17ee16a..250f80d 100755
--- a/autogen.sh
+++ b/autogen.sh
@@ -17,6 +17,18 @@ else
         gtkdocize || exit $?
 fi
 
+PKGCONFIG=`which pkg-config`
+if test -z "$PKGCONFIG"; then
+        echo "*** pkg-config not found, please install it ***"
+        exit 1
+fi
+
+pkg-config --print-errors gobject-introspection-1.0
+if [ $? != 0 ]; then
+       echo "You probably need to install 'libgirepository1.0-dev'"
+       exit 1
+fi
+
 # README and INSTALL are required by automake, but may be deleted by clean
 # up rules. to get automake to work, simply touch these here, they will be
 # regenerated from their corresponding *.in files by ./configure anyway.