llvmGen: Align objects in the data section

Objects in the data section may be referenced via tagged pointers.
Thus, align those objects to a 4- or 8-byte boundary for 32- or 64-bit
platforms, respectively.  Note, this may need to be reconsidered if
objects with a greater natural alignment requirement are emitted as e.g.
128-bit atomics.

Fixes #24163.