Splits off about half of suite/tests/api/ir_x86_4args_avx512_evex_mask_B.h into a new _C file to avoid an out-of-memory in VS2017 on Github Actions. The recent AVX-512 broadcast additions for #4534 (closed) in PR #4577 seem to have pushed it over the edge.
Issue: #4534 (closed), #4610 (closed), #4131 (closed), #4549 (closed) Fixes #4610 (closed)