Unlink aliases before creating anew

This caused some subtle issues, where aliases (e.g., "3.4") pointed
to one that was available when the package was created, but was
unavailable at the run time.

Author: BanzaiMan

bin/compile

@@ -25,7 +25,7 @@ sudo env PYTHON_BUILD_ROOT=/opt/pyenv/plugins/python-build \
   /opt/pyenv/plugins/python-build/bin/python-build $VERSION $INSTALL_DEST/$VERSION
 
 if [[ $ALIAS ]] ; then
-  sudo ln -s $INSTALL_DEST/$VERSION $INSTALL_DEST/$ALIAS
+  sudo ln -sf $INSTALL_DEST/$VERSION $INSTALL_DEST/$ALIAS
 fi
 
 # set up virtualenv arguments
@@ -44,7 +44,7 @@ virtualenv --distribute --python=$INSTALL_DEST/$VERSION/bin/python \
   $HOME/virtualenv/$VIRTENV_VERSION
 
 if [[ $ALIAS ]] ; then
-  ln -s $HOME/virtualenv/$VIRTENV_VERSION $HOME/virtualenv/python$ALIAS
+  ln -sf $HOME/virtualenv/$VIRTENV_VERSION $HOME/virtualenv/python$ALIAS
 fi
 
 $HOME/virtualenv/$VIRTENV_VERSION/bin/python -c "import sys; assert sys.maxunicode > 65535"