Reconstruct interpreter state before calling rb_ivar_get()

It could raise ractor exceptions. The included test didn't run properly
before this change.

bootstraptest/test_yjit.rb

@@ -2018,3 +2018,23 @@ assert_normal_exit %q{
   foo([1]) rescue nil
   foo([1]) rescue nil
 }
+
+# test ractor exception on when getting ivar
+assert_equal '42',  %q{
+  class A
+    def self.foo
+      _foo = 1
+      _bar = 2
+      begin
+        @bar
+      rescue Ractor::IsolationError
+        42
+      end
+    end
+  end
+
+  A.foo
+  A.foo
+
+  Ractor.new { A.foo }.take
+}

yjit_codegen.c

@@ -1571,11 +1571,13 @@ gen_get_ivar(jitstate_t *jit, ctx_t *ctx, const int max_chain_depth, VALUE compt
     //       inside object shapes.
     if (!RB_TYPE_P(comptime_receiver, T_OBJECT) ||
             rb_get_alloc_func(comptime_val_klass) != rb_class_allocate_instance) {
-        // General case. Call rb_ivar_get(). No need to reconstruct interpreter
+        // General case. Call rb_ivar_get().
-        // state since the routine never raises exceptions or allocate objects
-        // visibile to Ruby.
         // VALUE rb_ivar_get(VALUE obj, ID id)
         ADD_COMMENT(cb, "call rb_ivar_get()");
+
+        // The function could raise exceptions.
+        jit_prepare_routine_call(jit, ctx, REG1);
+
         mov(cb, C_ARG_REGS[0], REG0);
         mov(cb, C_ARG_REGS[1], imm_opnd((int64_t)ivar_name));
         call_ptr(cb, REG1, (void *)rb_ivar_get);