configure: Quote some shell variables.

From Dominik Vogt.


git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/trunk@216355 138bc75d-0d04-0410-961f-82ee72b054a4
Daily bump.

git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/trunk@216358 138bc75d-0d04-0410-961f-82ee72b054a4