unix/alloc: Map executable memory for code loading when needed.

This commit lets the Unix port use the new
MICROPY_PERSISTENT_CODE_LOAD_NATIVE configuration entry.

The Unix port needs to allocate memory with specific flags that let the
operating system run executable code from there.  This functionality was
gated behind the presence of a native emitter and thus its inclusion
condition had to be updated.

Signed-off-by: Alessandro Gatti <a.gatti@frob.it>

Author: agatti

ports/unix/alloc.c

@@ -32,7 +32,7 @@
 
 #include "py/mpstate.h"
 
-#if MICROPY_EMIT_NATIVE
+#if MICROPY_ENABLE_NATIVE_CODE
 
 #if defined(__OpenBSD__) || defined(__MACH__)
 #define MAP_ANONYMOUS MAP_ANON
@@ -80,4 +80,4 @@ void mp_unix_free_exec(void *ptr, size_t size) {
 
 MP_REGISTER_ROOT_POINTER(void *mmap_region_head);
 
-#endif // MICROPY_EMIT_NATIVE
+#endif // MICROPY_ENABLE_NATIVE_CODE