build: fix HAS_GI_DOCGEN never defined error

When building without --enable-bindings-glib configure reports this error:

  ...
  checking for help2man... true
  checking that generated files are newer than configure... done
  configure: error: conditional "HAS_GI_DOCGEN" was never defined.
  Usually this means the macro was only invoked conditionally.
  make: *** [Makefile:440: config.status] Error 1

Move the initialization of HAS_GI_DOCGEN outside the conditional
with_bindings_glib section so it is always initialized.

Fixes: e090088 ("bindings: add GLib bindings")
Signed-off-by: Kent Gibson <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Bartosz Golaszewski <[email protected]>

configure.ac

@@ -267,12 +267,12 @@ then
 		AC_MSG_ERROR([glib-mkenums not found - needed to build GLib bindings]))
 
 	AC_CHECK_PROG([has_gi_docgen], [gi-docgen], [true], [false])
-	AM_CONDITIONAL([HAS_GI_DOCGEN], [test "x$has_gi_docgen" = xtrue])
 	if test "x$has_gi_docgen" = xfalse
 	then
 		AC_MSG_NOTICE([gi-docgen not found - GLib documentation cannot be generated])
 	fi
 fi
+AM_CONDITIONAL([HAS_GI_DOCGEN], [test "x$has_gi_docgen" = xtrue])
 
 # GObject-introspection
 found_introspection=no