x86: Add a test for Clang unnamed sections

[FlorentRevest]

The origin object is the result of this file on a 6.18 build:

#include <linux/compiler.h>

void test_ubsan_out_of_bounds(void);
void test_ubsan_out_of_bounds(void)
{
	int i = 4, j = 4;
	volatile struct {
		char above[4];
		int arr[4];
		char below[4];
	} data;

	OPTIMIZER_HIDE_VAR(i);
	OPTIMIZER_HIDE_VAR(j);

	data.arr[j] = i;
}

And the patch is:

 void test_ubsan_out_of_bounds(void)
 {
-	int i = 4, j = 4;
+	int i = 4, j = -1; volatile struct { char above[4]; int arr[4];

Since Clang UBSAN generates "unnamed" sections, it exercises these sections changing.