Rationalize -mcpu for emulators, compilers and assemblers on ARM

Move SVE example in from arm-assembly-cheat.

atomic.cpp aarch64 add LSE ldadd placeholder, not compiling yet

build-baremetal

@@ -48,7 +48,6 @@ Build the baremetal examples with crosstool-NG.
         cc_flags = [
             '-I', self.env['root_dir'], LF,
             '-O{}'.format(self.env['optimization_level']), LF,
-            '-mcpu={}'.format(self.env['mcpu']), LF,
             '-nostartfiles', LF,
         ]
         if self.env['arch'] == 'arm':