Add dependency to intrinsics_gen

The IndVarSimplify pass in Polly uses the intrinsics header. We need to ensure
that the header is generated, before we use it. This patch fixes the problem
for the cmake build (it did not show up in the autoconf one).

Contributed by:   Sameer Sahasrabuddhe  <sameer.sahasrabuddhe@amd.com>

llvm-svn: 163130