[gegl-qt] Build: Allow to disable build of Python/PySide bindings

[Jon Nordby <jonnor src gnome org>]

commit 8376d991a15f4d1a30c076ecbdfa3118410cac44
Author: Jon Nordby <jononor gmail com>
Date:   Fri Sep 14 11:34:52 2012 +0200

    Build: Allow to disable build of Python/PySide bindings

 config.pri |   10 ++++++----
 1 files changed, 6 insertions(+), 4 deletions(-)
---
diff --git a/config.pri b/config.pri
index d115b14..b279869 100644
--- a/config.pri
+++ b/config.pri
@@ -104,10 +104,12 @@ contains(HAVE_QT_DECLARATIVE, no) {
     !build_pass:system(echo "QtDeclarative not found - no QML support")
 }
 
-HAVE_PYSIDE = yes
-!system(pkg-config pyside){
-    !build_pass:system(echo "PySide not found - no Python support")
-    HAVE_PYSIDE = no
+isEmpty(HAVE_PYSIDE) {
+    HAVE_PYSIDE = yes
+    !system(pkg-config pyside){
+        !build_pass:system(echo "PySide not found - no Python support")
+        HAVE_PYSIDE = no
+    }
 }
 
 # Can go away when PySide supports Qt5