ARM for linux

Until now, ARM architectures are only allowed for Darwin systems. This MR extends their usage to Linux systems.

pystencils/backends/simd_instruction_sets.py

@@ -43,7 +43,8 @@ def get_supported_instruction_sets():
         return _cache.copy()
     if 'PYSTENCILS_SIMD' in os.environ:
         return os.environ['PYSTENCILS_SIMD'].split(',')
-    if platform.system() == 'Darwin' and platform.machine() == 'arm64':  # not supported by cpuinfo
+    if (platform.system() == 'Darwin' or platform.system() == 'Linux') and platform.machine() == 'arm64':
+        # not supported by cpuinfo
         return ['neon']
     elif platform.system() == 'Linux' and platform.machine().startswith('riscv'):  # not supported by cpuinfo
         libc = CDLL('libc.so.6')