Propagate SWITCH_RATIO to DYNAMIC_ARCH builds

SWITCH_RATIO for Arm(R) Neoverse(TM) architecture

Fix instabilities in CGEMM/CTRMM/DNRM2 on Apple M1/M2 under OSX

Remove any stray trailing dash from CROSS_SUFFIX

This seems like a good balance of values for reasonably sized matrices. With `SWITCH_RATIO=16` the DGEMM scales better to bigger sizes but the better solution would be some kind of
thread throttling so I've gone with `SWITCH_RATIO=8`.

Previously dynamic builds were either using the default SWITCH_RATIO
or one from the higher level architecture; this patch ensures the
dynamic builds can use this parameter as well.

Add Chris Sidebottom to CONTRIBUTORS.md

parallel build fixes

Fix ?GEMMT implementation

fix missing blank in c_check

Fix x86 detection error

Convert CMAKE booleans to 0/1 values for gensymbol

Support Apple A15/M2 cpus through the existing VORTEX target

Protect CROSS_SUFFIX against spurious linebreaks from isolated dashes

fix for #3989

Export `ssyconvf` symbol

This was apparently missed in commit a836fe8ec when adding the
LAPACK 3.7.0 symbols. We noticed when adding wrappers for 3.7.0
routines in SciPy. For more details, see
https://github.com/rgommers/scipy/issues/143

Refactor ?GEBAL for readability (Reference-LAPACK PR 808)

Add Apple M1 testing via Cirrus CI