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

Assisted-by: GLM 5.3

verify/testdata/linkreg_loong64.s

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+// 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 loong64, the amd64 one's sibling:
+// stack discipline (add), an intra-file call (probe calling seven,
+// R_CALLLOONG64), a PCALAU12I pair against static data (word<>,
+// R_LOONG64_ADDR_HI/LO), 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 (R3), the loong64 ABI0 frame convention.
+
+// func add(a, b int64) int64
+TEXT ·add(SB), NOSPLIT, $0-24
+	MOVV a+0(FP), R4
+	MOVV b+8(FP), R5
+	ADDV R5, R4, R4
+	MOVV R4, ret+16(FP)
+	RET
+
+// func seven() int64
+TEXT ·seven(SB), NOSPLIT, $0-8
+	MOVV $7, R4
+	MOVV R4, ret+0(FP)
+	RET
+
+// func probe() int64 = seven() + word<>(SB)
+TEXT ·probe(SB), NOSPLIT, $8-8
+	CALL ·seven(SB)
+	MOVV 8(R3), R4
+	MOVV word<>(SB), R5
+	ADDV R5, R4, R4
+	MOVV R4, ret+0(FP)
+	RET
+
+// func entryAddr() uintptr
+TEXT ·entryAddr(SB), NOSPLIT, $0-8
+	MOVV entry(SB), R4
+	MOVV R4, ret+0(FP)
+	RET
+
+// func counterVal() int64
+TEXT ·counterVal(SB), NOSPLIT, $0-8
+	MOVV counter(SB), R4
+	MOVV 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