Using the have_neon boolean to enable NEON code means we have to either
fully enable it or fully disable it. When using -Dneon=runtime, ideally
only the parts that support runtime checks would be built for NEON, and
those that don't would be built without NEON. Though, there are no
longer any runtime checks for NEON anywhere, so it's equivalent to 'no'
with a warning.
In general, we should use have_* variables to indicate compiler support,
and *_opt options to choose if and how we want to utilize that. Use
neon_opt to control NEON compilation and avoid modifying have_neon which
now would fully refer to compiler support.
Signed-off-by: Alper Nebi Yasak <alpernebiyasak@gmail.com>
