[cmake] Pass LLVM_TEMPORARILY_ALLOW_OLD_TOOLCHAIN to NATIVE configure

We should propagate this down to host builds so that e.g. people using
an optimized tablegen can do the sub-configure successfully.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@353463 91177308-0d34-0410-b5e6-96231b3b80d8
1 file changed