autogen.sh: Honor NOCONFIGURE=1

See http://people.gnome.org/~walters/docs/build-api.txt

Hdg: I know this may seem unnecessary since we also have bootstrap.sh, but
the Gnome people are doing continues build testing of Gnome + dependencies
and having all autogen.sh scripts support NOCONFIGURE=1 makes live easier for
them. Note that in return we get "free" continues build-testing and patches
and / or a heads up when we break things.

Signed-off-by: Hans de Goede <hdegoede@redhat.com>
diff --git a/autogen.sh b/autogen.sh
index 591f7ab..ab87fb3 100755
--- a/autogen.sh
+++ b/autogen.sh
@@ -3,4 +3,6 @@
 set -e
 
 ./bootstrap.sh
-./configure --enable-maintainer-mode --enable-examples-build --enable-tests-build "$@"
+if test -z "$NOCONFIGURE"; then
+    exec ./configure --enable-maintainer-mode --enable-examples-build --enable-tests-build "$@"
+fi