[gobject-introspection] giscanner: Don't run pkg-config when there's no packages specified

[Johan Dahlin <johan src gnome org>]

commit 639c4ed8f42dbed31a4fda8f56c25ef42e9f415f
Author: Jasper St. Pierre <jstpierre mecheye net>
Date:   Tue Mar 27 13:18:54 2012 -0300

    giscanner: Don't run pkg-config when there's no packages specified
    
    This prevents a simple error from pkg-config, "Must specify package names
    on command line"
    
    https://bugzilla.gnome.org/show_bug.cgi?id=673668

 giscanner/scannermain.py |    7 ++++---
 1 files changed, 4 insertions(+), 3 deletions(-)
---
diff --git a/giscanner/scannermain.py b/giscanner/scannermain.py
index bcacd0f..794cede 100755
--- a/giscanner/scannermain.py
+++ b/giscanner/scannermain.py
@@ -405,9 +405,10 @@ def scanner_main(args):
 
     packages = set(options.packages)
     packages.update(transformer.get_pkgconfig_packages())
-    exit_code = process_packages(options, packages)
-    if exit_code:
-        return exit_code
+    if packages:
+        exit_code = process_packages(options, packages)
+        if exit_code:
+            return exit_code
 
     ss = create_source_scanner(options, args)