Use XCODEFLAGS in order to set MACOSX_DEPLOYMENT_TARGET

Author: splhack

.travis.yml

@@ -11,6 +11,7 @@ compiler:
 
 env:
   - MACOSX_DEPLOYMENT_TARGET=10.8
+    XCODEFLAGS="MACOSX_DEPLOYMENT_TARGET=10.8"
     VERSIONER_PERL_VERSION=5.18
     VERSIONER_PYTHON_VERSION=2.7
     vi_cv_path_python=/usr/bin/python