Make MICROPY_CPYTHON_COMPAT settable

Author: DavePutz

py/circuitpy_mpconfig.h

@@ -188,7 +188,9 @@ typedef long mp_off_t;
 
 // Turning off FULL_BUILD removes some functionality to reduce flash size on tiny SAMD21s
 #define MICROPY_BUILTIN_METHOD_CHECK_SELF_ARG (CIRCUITPY_FULL_BUILD)
+#ifndef MICROPY_CPYTHON_COMPAT
 #define MICROPY_CPYTHON_COMPAT                (CIRCUITPY_FULL_BUILD)
+#endif
 #define MICROPY_PY_BUILTINS_POW3              (CIRCUITPY_BUILTINS_POW3)
 #define MICROPY_COMP_FSTRING_LITERAL          (MICROPY_CPYTHON_COMPAT)
 #define MICROPY_MODULE_WEAK_LINKS             (0)