py/nativeglue: Remove dependency on mp_fun_table in dyn-compiler mode.

mpy-cross uses MICROPY_DYNAMIC_COMPILER and MICROPY_EMIT_NATIVE but does
not actually need to execute native functions, and does not need
mp_fun_table.  This commit makes it so mp_fun_table and all its entries are
not built when MICROPY_DYNAMIC_COMPILER is enabled, significantly reducing
the size of the mpy-cross executable and allowing it to be built on more
machines/OS's.
diff --git a/py/mpconfig.h b/py/mpconfig.h
index 219f8de..4172e17 100644
--- a/py/mpconfig.h
+++ b/py/mpconfig.h
@@ -338,6 +338,7 @@
 #endif
 
 // Whether the compiler is dynamically configurable (ie at runtime)
+// This will disable the ability to execute native/viper code
 #ifndef MICROPY_DYNAMIC_COMPILER
 #define MICROPY_DYNAMIC_COMPILER (0)
 #endif