feat(dist): Win32 POSIX shim for el_runtime.c cross-compilation

dist/win32_shim.h

@@ -0,0 +1,35 @@
+/*
+ * win32_shim.h — Extra POSIX→Win32 stubs for cross-compiling el_runtime.c with mingw-w64.
+ * Injected via -include; supplements el_platform_win.h for symbols it doesn't yet cover.
+ */
+#ifdef _WIN32
+#include <windows.h>
+
+/* ── rusage / getrusage ────────────────────────────────────────────────────── */
+/* el_runtime.c uses getrusage(RUSAGE_SELF) only for a soft memory guard.
+ * On Windows, stub it out: always return 0 ru_maxrss so the guard never fires. */
+#ifndef RUSAGE_SELF
+#define RUSAGE_SELF 0
+struct rusage {
+    long ru_maxrss;   /* the only field el_runtime actually reads */
+};
+static inline int getrusage(int who, struct rusage *r) {
+    (void)who;
+    if (r) r->ru_maxrss = 0;
+    return 0;
+}
+#endif /* RUSAGE_SELF */
+
+/* ── fsync ─────────────────────────────────────────────────────────────────── */
+/* Windows has FlushFileBuffers but no fsync; map it. */
+#ifndef fsync
+#include <io.h>
+static inline int el_win_fsync(int fd) {
+    HANDLE h = (HANDLE)_get_osfhandle(fd);
+    if (h == INVALID_HANDLE_VALUE) return -1;
+    return FlushFileBuffers(h) ? 0 : -1;
+}
+#define fsync(fd) el_win_fsync(fd)
+#endif /* fsync */
+
+#endif /* _WIN32 */