Revert "Create presym files for each build target" (58ba883e)

Due to the above changes, it may not work with the existing build
configurations in cross-compilation (even if we can build without presym),
therefore revert it once (ref https://github.com/mruby/mruby/pull/5202#issuecomment-735412643). Sorry for the lack of consideration.

src/symbol.c

@@ -20,7 +20,7 @@ static const struct {
   const char *name;
   uint16_t len;
 } presym_table[] = {
-#include <mruby/presym.inc>
+#include <../build/presym.inc>
 };
 
 static mrb_sym