Add Ruby 2.7.5 patches

patches/ruby/2.7.5/debug-segfault.patch

@@ -0,0 +1,25 @@
+diff --git a/class.c b/class.c
+index c866d1d727..37ff3c5ade 100644
+--- a/class.c
++++ b/class.c
+@@ -27,6 +27,7 @@
+ #include "ruby/st.h"
+ #include "constant.h"
+ #include "vm_core.h"
++#include "vm_debug.h"
+ #include "id_table.h"
+ #include <ctype.h>
+ 
+@@ -119,6 +120,12 @@ rb_class_foreach_subclass(VALUE klass, void (*f)(VALUE, VALUE), VALUE arg)
+     while (cur) {
+ 	VALUE curklass = cur->klass;
+ 	cur = cur->next;
++
++	if (curklass == 0) {
++		fprintf(stderr, "=== Detected NULL subclass:\n");
++		dp(curklass);
++	}
++
+ 	f(curklass, arg);
+     }
+ }