The cc-rs crate will try to guess the host compiler and use default
flags these are not specifically set. The default behavior is wrong in
Void cross-compilation environments. Explicitly define HOST_CC=gcc and
use innocuous HOST_CFLAGS=-O2 just to thwart the bad defaults.
Co-authored-by: Érico Rolim <erico.erc@gmail.com>
Co-authored-by: Andrew J. Hesford <ajh@sideband.org>
Closes: #28416.