[OpenMP] Naturally align internal global variables in the OpenMPIRBuilder

We use this helper to make several internal global variables during
codegen. currently we do not specify any alignment which allows the
alignment to be set incorrectly after some changes in how alignment was
handled. This patch explicitly aligns these variables to the natural
alignment as specified by the data layout

Fixes https://github.com/llvm/llvm-project/issues/62668

Reviewed By: tianshilei1992, gchatelet

Differential Revision: https://reviews.llvm.org/D150461