Add native Portduino malloc shim (#10677)

* Add native Portduino malloc shim

* Taking copilots advice

Honestly I don't think it matters that much, but if it makes copilot happy, return ret if something weird happens.

Co-authored-by: Copilot Autofix powered by AI <175728472+Copilot@users.noreply.github.com>

---------

Co-authored-by: Ben Meadors <benmmeadors@gmail.com>
Co-authored-by: Copilot Autofix powered by AI <175728472+Copilot@users.noreply.github.com>

variants/native/portduino/malloc.h

@@ -0,0 +1,21 @@
+#pragma once
+
+#if defined(__APPLE__)
+#include <malloc/malloc.h>
+#include <stdlib.h>
+#include <errno.h>
+
+// LovyanGFX includes the Linux header name; bridge it for Darwin native builds.
+static inline void *memalign(size_t alignment, size_t size)
+{
+    void *ptr = NULL;
+    int ret = posix_memalign(&ptr, alignment, size);
+    if (ret != 0) {
+        errno = ret;
+        return NULL;
+    }
+    return ptr;
+}
+#else
+#include_next <malloc.h>
+#endif