test(verify): gate GOOBJ link parity with cmd/link

Assisted-by: GLM 5.3

verify/testdata/linkreg_arm64.s

@@ -0,0 +1,57 @@
+// Copyright (c) 2026 Petr Balvín <opensource@petrbalvin.org> (https://petrbalvin.org)
+// SPDX-License-Identifier: BSD-3-Clause
+
+#include "textflag.h"
+
+// The link-regression kernel for arm64, the amd64 one's sibling: stack
+// discipline (add), an intra-file branch with link (probe calling seven,
+// R_CALLARM64), an ADRP+ADD pair against static data (word<>,
+// R_ADDRARM64), a symbol-valued DATA field (entry holding seven's
+// address, R_ADDR), NOPTR data outside the GC's type scan (counter) and
+// the data section itself.  The callee's result slot sits at the caller's
+// SP+8, the arm64 ABI0 frame convention.
+
+// func add(a, b int64) int64
+TEXT ·add(SB), NOSPLIT, $0-24
+	MOVD a+0(FP), R0
+	MOVD b+8(FP), R1
+	ADD  R1, R0, R0
+	MOVD R0, ret+16(FP)
+	RET
+
+// func seven() int64
+TEXT ·seven(SB), NOSPLIT, $0-8
+	MOVD $7, R0
+	MOVD R0, ret+0(FP)
+	RET
+
+// func probe() int64 = seven() + word<>(SB)
+TEXT ·probe(SB), NOSPLIT, $8-8
+	BL   ·seven(SB)
+	MOVD 8(RSP), R0
+	MOVD $word<>(SB), R4
+	MOVD (R4), R5
+	ADD  R5, R0, R0
+	MOVD R0, ret+0(FP)
+	RET
+
+// func entryAddr() uintptr
+TEXT ·entryAddr(SB), NOSPLIT, $0-8
+	MOVD entry(SB), R4
+	MOVD R4, ret+0(FP)
+	RET
+
+// func counterVal() int64
+TEXT ·counterVal(SB), NOSPLIT, $0-8
+	MOVD counter(SB), R4
+	MOVD R4, ret+0(FP)
+	RET
+
+GLOBL word<>(SB), RODATA, $8
+DATA word<>+0(SB)/8, $0x0fedcba987654321
+
+GLOBL entry(SB), RODATA, $8
+DATA entry+0(SB)/8, $·seven(SB)
+
+GLOBL counter(SB), NOPTR, $8
+DATA counter+0(SB)/8, $1234