Change extra copy of musl patch into a symlink.

steps/musl-1.1.24/patches-pass3/madvise_preserve_errno.patch

@@ -1,15 +0,0 @@
-# SPDX-FileCopyrightText: 2023 Richard Masters <grick23@gmail.com>
-# SPDX-License-Identifier: MIT
-diff -r -u musl-1.1.24.orig/src/malloc/malloc.c musl-1.1.24/src/malloc/malloc.c
---- src/malloc/malloc.c	2019-10-13 21:58:27.000000000 +0000
-+++ src/malloc/malloc.c	2023-12-22 23:18:21.088570834 +0000
-@@ -496,7 +496,9 @@
- 		uintptr_t a = (uintptr_t)self + SIZE_ALIGN+PAGE_SIZE-1 & -PAGE_SIZE;
- 		uintptr_t b = (uintptr_t)next - SIZE_ALIGN & -PAGE_SIZE;
- #if 1
-+		int e = errno;
- 		__madvise((void *)a, b-a, MADV_DONTNEED);
-+		errno = e;
- #else
- 		__mmap((void *)a, b-a, PROT_READ|PROT_WRITE,
- 			MAP_PRIVATE|MAP_ANONYMOUS|MAP_FIXED, -1, 0);

steps/musl-1.1.24/patches-pass3/madvise_preserve_errno.patch

@@ -0,0 +1 @@
+../patches/madvise_preserve_errno.patch