musl: introduce dummy functions for mallinfo(), malloc_info(), and malloc_trim()

These functions are not provided by musl.

src/include/musl/malloc.h

@@ -0,0 +1,39 @@
+/* SPDX-License-Identifier: LGPL-2.1-or-later */
+#pragma once
+
+#include <errno.h>
+#include <stdio.h>
+
+/* struct mallinfo2 will be defined and struct mallinfo is converted to struct mallinfo2 in
+ * override/malloc.h. Hence, here we define struct mallinfo. */
+
+struct mallinfo {
+        int arena;    /* non-mmapped space allocated from system */
+        int ordblks;  /* number of free chunks */
+        int smblks;   /* number of fastbin blocks */
+        int hblks;    /* number of mmapped regions */
+        int hblkhd;   /* space in mmapped regions */
+        int usmblks;  /* always 0, preserved for backwards compatibility */
+        int fsmblks;  /* space available in freed fastbin blocks */
+        int uordblks; /* total allocated space */
+        int fordblks; /* total free space */
+        int keepcost; /* top-most, releasable (via malloc_trim) space */
+};
+
+static inline struct mallinfo mallinfo(void) {
+        return (struct mallinfo) {};
+}
+
+static inline int malloc_info(int options, FILE *stream) {
+        if (options != 0)
+                errno = EINVAL;
+        else
+                errno = EOPNOTSUPP;
+        return -1;
+}
+
+static inline int malloc_trim(size_t pad) {
+        return 0;
+}
+
+#include_next <malloc.h>