[Targets] Add errors for tiny and kernel codemodel on targets that don't support them

Adds fatal errors for any target that does not support the Tiny or Kernel
codemodels by rejigging the getEffectiveCodeModel calls.

Differential Revision: https://reviews.llvm.org/D50141


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@348585 91177308-0d34-0410-b5e6-96231b3b80d8
27 files changed