[Win64] Make sure ninja is built in 64bit mode as well.

Change-Id: If1665b5bb7a6db07ca737aa00d0ddba964e418aa
Reviewed-by: Michael Bruning <michael.bruning@digia.com>
Reviewed-by: Andras Becsi <andras.becsi@digia.com>

tools/qmake/mkspecs/features/functions.prf

@@ -113,7 +113,11 @@ defineReplace(findOrBuildNinja) {
 
     # If we did not find ninja, then we bootstrap it.
     !exists($$out) {
-        system("python $$dirname(out)/bootstrap.py")
+        contains(DEFINES, WIN64) {
+          system("python $$dirname(out)/bootstrap.py --x64")
+        } else {
+          system("python $$dirname(out)/bootstrap.py")
+        }
     }
     return($$out)
 }